Anthony Hope.

Conchological miscellany (Volume 7) online

. (page 1 of 26)
Online LibraryAnthony HopeConchological miscellany (Volume 7) → online text (page 1 of 26)
Font size
QR-code for this ebook




. (00.


. (2 CL







<, '- YV14^*-*^VA-

[ 165 ]



X. 0# the Relations of Tanalia, Philopotamis, and Paludomus ; with a review of the
Cingalese Species of the latter Genera, By H. P. BLANFOKD, F. G.S. Communicated
by Dr. J. D. HOOKER, F.H.S., F.L.S., fyc.

(Plate XXVII.)

Read June 18th, 1863.

a paper read at the meeting of this Society in June last, I expressed an opinion that
the Cingalese genera Tanalia and Philopotamis* are more closely related to Melania than
has been held by several recent writers, and that in fact they should be regarded rather
as sections of that genus than as distinct genera. The object of the first part of the
present paper is to substantiate that view by showing that the opercula of Philopotamis
and Tanalia, upon the structure of which generic distinction has been based, so far from
being distinct in type, really present modifications of the subspiral operculum of Melania,
from which the digression is serial and gradated in the different forms (species and
varieties) included under those genera. While, however, insisting on the facts of affinity,
I should at the outset so far modify the above general assertion as to admit that the
question of genus and subgenus is to a great extent one of opinion, depending upon what
amount of difference be held to constitute a family, genus, or subgenus. By those who
regard such a form as Melania variabilis, Bens., with its largely spiral operculum, as a
true Melania, Philopotamis and Tanalia should be treated as subgenera, their aberration
in one direction from the type not being greater than that of M. variabilis in another
direction. To those, on the contrary, who, with Messrs. Gray and Adams, regard most of
the Lamarckian genera as families, Philopotamis, &c., will rank with the typical Melanias
as nearly allied genera of one family.

In the second part of the paper I shall review the Cingalese species of Paludomus and
Philopotamis ; the latter genus is, so far as we know at present, restricted to Ceylon.


It is unnecessary to review in detail the various opinions that have been expressed with
regard to the affinities of Tanalia, Philopotamis, and Paludomus. The last-mentioned
genus was distinguished from Melania by Swainson on account of the concentric structure
of the operculum, and Tanalia and Philopotamis were subsequently separated therefrom
by Gray and Layard, the former genus having a trigonal operculum with a marginal
nucleus, the latter a subspiral operculum with a submarginal nucleus. Paludomus

* Paludomus was also included in this remark, but reconsideration leads me to regard it as more distinct than either
of the above. See posted. :rr * \*i-\ /* f * '7



conicus, Gray, Tanalia aculeata, Chemn., and PUlopotamis sulcata, Reeve, sp., are quoted
as the respective types of the genera.

Two other genera have been formed from the species herein included, viz. Rivulina,
Lea, and Gang a, Layard; but there appears to be no distinction between the former
genus and Paludomus, the two species quoted under it being, so far as I can judge from
Mr. Cuming's authentic specimens, mere varieties of Paludomus chilinoides, Reeve, and
P. Taujoriensis, Chemn., while the latter is, as I have shown in my former communica-
tion, founded upon certain monstrous forms of Tanalia aculeata.

In the June Number of the ' Ann. & Mag. Nat. Hist.' for 1856, Mr. Benson pointed out
that although the adult operculum of Paludomus has, as stated, a concentric structure,
much resembling that of Paludina, with which the genus had consequently been classed
by Dr. Gray, and subsequently by Mr. A. Adams, the embryonic operculum or the nucleus
of the adult is spiral, resembling that of a Melania. He also remarked that the subspiral
structure of the operculum of Philopotamis indicated an affinity with Melania, but ex-
pressed a doubt whether Tanalia, with its unguiculate operculum, should be referred to
the Paludomidae at all.

Now remembering that no essential difference of structure has been noticed in the
animals of these genera, and that, with the exception of certain differences of habit, upon
which I shall remark presently, the only assigned generic characters held to distinguish
them from each other and from Melania are those of the operculum, let us see what these
i -ally amount to. PL XXVII. fig. 8 represents, on an enlarged scale, the operculum
of a Ceylonese specimen of Melania spinulosa, Lamk., a common Eastern species, and,
on the point in question, a fair representative of the genus. The structure is paucispiral,
and the nucleus subbasal. Fig. 9 is the operculum of M. lirata, Bens., also enlarged : in
this the structure is less distinctly spiral, and the nucleus is almost marginal and basal.
In fig. 13, the operculum of Tanalia violacea, Layard, a subspiral structure is still appa-
rent, but the nucleus is marginal and dextrally subbasal. The operculum of Philopotamis
decussatct, Reeve, fig. 10, only differs from this last in having the spiral structure more
distinctly developed. And, finally, from T. violacea we pass to T. aculeata, fig. 14, in
which a trace of a subspiral structure is only perceptible towards the nucleus ; while
from Ph. decussata we proceed through Ph. sulcata, fig. 11, to Ph. globulosa, figs. 12 a & b,
which is the most aberrant form presented in the genus. We have thus tolerably perfect
series from the typical Melania operculum to the extreme forms of Philopotamis and
Tanalia. The operculum of Ph. nigricans, Eeeve, is more nearly related to that of
Melania than any of the above, and indeed some forms are scarcely distinguishable
generically : fig. 15 a affords an instance of this ; but in others again the Philopotamis
structure is more developed (fig. 15 b).

It might seem at first sight that the operculum of Paludomus is, in an abstract mor-
phological point of view, merely that of a Philopotamis with the nucleus pushed over
towards the other side; but it is, I think, essentially different, or rather, the digression
from the Melania type of structure has taken place in a different direction. The passage
from Melania spinulosa to Tanalia aculeata may be regarded as a gradual unrolling of
the opercular spiral, which becomes nearly obsolete by successive gradations, while in


Philopotamis a similar modification obtains to a less extent, accompanied in Ph. glo-
bulosa with an incipient concentric growth. In Paludomus, on the other hand, the
growth of the operculum is, up to a certain point, that of a typical Melania : after the
formation of one and a half or two whorls it suddenly takes a different direction, and is
superseded by a strictly concentric growth, in which the chief addition is in the direction
of the outer or dextral margin instead of the inner as in Melania, Philopotamis, and
Tanalia. It would be arguing in a circle, and on an unproved generalization, to adduce
the comparatively wide range of Paludomus, as contrasted with that of Philopotamis and
Tanalia, in support of their generic diversity, on the supposition that successive grada-
tions of structural character argue successive appearance in time, and that the earlier
forms have the wider range ; but if the structural argument appear valid, the facts of
range will have much significance to those who admit the possibility of generic derivation
from preexisting types.

The solid structure and depressed form of the shells of Paludomus, Tanalia, and Phi-
lopotamis may be held to indicate a closer relationship between these genera than exists
between any one of them and Melania. In these respects, however, the true Melanias
exhibit much variety. Paludomus brevis, D'Orb., is a Melania as regards its operculum,
although the shell has, on account of its form, been erroneously referred to Paludomus ;
and the Melania Hugelii* of S. India is almost as thick and depressed as certain Paludomi.
The genus Gyrotoma also, with the operculum of Melania, has the solid, depressed form
of Paludomus, yet would scarcely be classed therewith.

With respect to habit, no marked line can be drawn between the different genera in
question. Tanalia aculeata is indeed never found in still water, nor, I believe, elsewhere
than in mountain streams ; but it is met with in the smallest perennial streamlets as well
as in the largest torrents : it is generally found adhering to rocks, but also frequently
crawling over sandy bottoms. Philopotamis globulosa has a similar range of habit, but
is apparently more restricted in geographical range. I have myself only met with it in
the Mahavelli Ganga and tributaries, and in the stream of the Balcadua Pass, nor have
I seen any specimens from the southern or eastern watershed of the hills. Ph. sulcata
occurs chiefly in the smaller streams on and among the hills, extending from an elevation
but little above the sea to a height of 3000 feet. Mr. Layard records that this species
sometimes climbs far out of the water ; but, though I do not question his accuracy, I do
not remember ever to have met with it myself in such a situation. The species of
Paludomus are, as their name imports, the most marsh-loving in their habits; but
P. chilmoides and P. Tanjoriensis, the only species I have myself collected, though
occurring in marshes and tanks, are at least equally or even more common in streams
and rivers, of both slow and rapid flow, on the hills and in the low country.

* This species is from the upper waters of the Cauvery, where it has been rediscovered by Dr. Jerdon. The quoted
habitat, New Holland, is probably erroneous.



Genus MELANIA, Lamk.
Subgenus PHILOPOTAMIS, Layard.

Eive species of this genus are known to me, one of which, P. regalis, Layard, is
doubtful, and may hereafter prove to be merely a variety of P. sulcata : of another,
P. decitssata, Reeve, I have only seen the three specimens in Mr. Cuming's collection,
and, in a genus exhibiting so much specific variation as the present, a much larger series
is necessary to convince me of specific distinction. The other three species are more
distinct from each other than is usual in the case of the allied subgenera, and differ to
some extent in their opercular structure, as well as in the form, &c. of their shells. Each
of these species is variable, and one includes several forms which have been described as
distinct. The following is a list of the species provisionally admitted by me :

P. sulcata, Ueeve. P. nigricans, Reeve.

P. regalis, Layard. P. decussata, Reeve.

P. globulosa, Gray.

PHILOPOTAMIS SULCATA, Reeve. (PI. XXVII. figs. 5 a-c, 11.)

Shell ovately conic or conic, more or less strongly sulcate; sulcations regular,
frequently minutely decussated by transverse striae, sometimes nearly obsolete. Epidermis
citrine to dark brown or reddish brown, concealing the proper colouring of the shell,
which consists sometimes of irregular zigzags, more or less interrupted, and tending
towards a spiral arrangement ; more frequently of spiral bands, interrupted or continuous.
Spire elevated, varying in height, always eroded. Upper whorls (rarely more than three
remaining) variable in convexity, rounded or flattened. Last whorl globose or (rarely)
conoidal. Aperture gibbous to obliquely pyriform. Outer lip denticulated. Inner lip
thinly callous : columella flattened, arcuated, and somewhat everted, sometimes tinted
with In-own. Opcrculum ovately pyriform, varying in width, obsoletely spiral : nucleus
very near the dextral margin, somewhat variable in position.

r l'li is species is the type of the genus. The shell is always Paludiniform, but varies in
globosity even in a series of specimens from the same spot. PI. XXVII. figs. 5 a & b are
two specimens from the same stream at Avisavella, the first being the most tumid form
I have seen. Pig. 5 c is a very conical form, from Hautanne, a hill in the neighbourhood
of Kandy. In fig. 5 a it will be seen that the sutures are deep, the upper part of the
whorl sloping off much less obtusely than in fig. 5 b. Other specimens in my collection
present intermediate gradations, so that it is impossible to regard these differences as
other than specific variations. The spiral sulcation, from which the species derives its
name, is usually fine and regular, and in some specimens is seen under the lens to be
regularly decussated with stria3 of growth. In other specimens these last are obsolete,
ifl occasionally the spiral sulcation also to a great extent, at least on the last portion of
the body-whorl. The upper whorls are always more or less eroded.

The painting of the shell varies greatly. In a specimen from Avisavella the whole is


covered with a zigzag marbling, but more frequently this is broken up into inter-
rupted spiral bands, and in other specimens, again, the bands are continuous, resembling
those which characterize P. bicincta, but narrower and more numerous. The colouring is
only visible in the interior, and, in old specimens, is concealed beneath a white callous
deposit of the mantle. The edge of the peristome is generally, but not always, tinted
with brown.

The operculum is normally as figured in Plate XXVII. fig. 11, but, as in the case of
Tanalia, is not unfrequently destroyed, and replaced by one having a concentric structure.
If this takes place at an early age, the nuclear portion of the operculum is alone so
formed, the later-formed layers having the usual arrangement. I found that, in a
stream at Hautanne, more than half the specimens had lost portions of their opercula,
and one or two full-grown shells were totally divested of this appendage. The shells of
these specimens were also eroded in holes in a manner difficult to account for.


This appears to be a rare shell. I saw no specimens of it in Major Skinner's collec-
tion, nor have I met with it myself in Ceylon. The only specimens I have seen were
those in Mr. Hugh Cuming's collection, obtained, I believe, by Mr. Thwaites. I am
thus unable to add anything to Mr. Layard's description from my own observations ; but
I may remark that it appears to differ in no respect from P. sulcata, except in possessing
a row of small scale-like spines round the upper edge of the whorl. I cannot but think
that it may eventually prove to be a variety of P. sulcata.

PHILOPOTAMIS GLOBULOSA, Gray. (PL XXVII. figs. 1 a-e, 12 a, b.)
P. abbreviata, Reeve; P. bicincta, Reeve; P. clavata, Reeve.

Shell globose or ovate, solid, smooth, rarely bearing faint traces of spiral sulci.
Epidermis yellowish brown. Shell colourless, or ornamented with two or three spiral
bands, only visible in the interior of adult shells. Spire depressly conical, variable in
height ; apex usually eroded. Whorls flattened, the last more or less elongated, depressly
flattened above, produced below. Aperture semi-ovate to obliquely pyriform, subcanali-
culate behind, lined interiorly with a callus, sometimes tinted yellow towards the exterior
margin. Outer lip sharp. Columella callous, arcuated towards the front. The callus
continuous to the junction of the outer lip. Operculum obliquely pyriform, obsoletely
spiral, subconcentric : nucleus rather variable in position near the dextral margin, and
from ^th to f ths the height of the operculum.

The shell of this species is always yellowish brown (the colour of the epidermis), and
shows less tendency to variation than most of its allies. The chief points of variation
observable are the form, which is sometimes globose, sometimes elongate (but exhibit-
ing all intermediate gradations) ; and the painting, which is sometimes developed, more
frequently not, and in the former case only in the interior of the adult shell. Two
extreme] forms have been described as P. globulosa and P. bicincta, but the comparison
of even a moderate series from Kandy, Ambegammoa, and the Balcadua Pass is sufficient,
I think, to convince any one that they are specifically identical. In some small specimens


from Peradinia, near Kandy, the upper whorls are in certain of the specimens somewhat
exserted, but only to a slight degree. In the more elongate forms the slight flattening
and angulation of the upper part of the whorls which characterize the more glo
specimens tend to become obsolete.

Coloured specimens, which are almost always young shells, have sometimes two, some

times three bands.

The operculum of this species is characterized by its more pyriform shape than that
Philopotamis mlcata, and by the nucleus being further from the margin. The position
of the latter is somewhat variable (see fig. 12 a, b).

Pa/udomus olicaceus, Reeve, from Sumatra, bears much resemblance to this species ;
but, in the absence of its operculum, no safe conclusion can be drawn.

PHILOPOTAMIS NIGRICANS, B/eeve. (PI. XXVII. figs. 3 a-e, 15 , 6.)

Shell of type-form, thick, elevately conical (apical whorls almost invariably eroded),
ornamented with close-set granular striae, those near the suture more developed than
the rest. Colour of epidermis dark citrine to black. The shell painted with numerous
wavy brown bands, generally visible only in the interior, and sometimes obsolete near the
aperture. Spire, when perfect, acutely conical ; whorls about six, rarely more than three
remaining in eroded shells, flattened, with shallow sutures. Last whorl more or less
angulate at the periphery, obliquely flattened beneath. Aperture obliquely ovate,
pointed above. Peristome white or greyish white, callous: outer lip sharp, even:
columella slightly arcuated anteriorly. Operculum paucispiral : nucleus rather large,
transversely central, and at from Jth to fths of the height.

Var. a. (The only specimens found, not fully grown.) Shell in form as above, uneroded,
smooth, with one or two strong striae only near the suture. Epidermis transparent,
citrine, with the markings of the shell distinctly visible through it.

? Var. /3. Form of shell as above, but more elongate. Shell'smooth, colourless or with
the bands broken up into a series of square dots. Last whorl elongate, the angulation
nearly or quite obsolete (PL XXVII. fig. 3 e).

This species is more nearly allied to Melania, both in form and in the structure of the
operculum, than any of its allies. From P. decussata, the only congener to which it
bears any near resemblance, it is distinguished by its more conical form, the angularity
of the last whorl, and the character of the marking, as well as, in the majority of speci-
mens, by the granular surface, which, so far as I have seen, is peculiar to this species.

The type-forms and the var. a. were collected by myself in large numbers (associated
with Tanalia violacea) in some small mountain streams near Huckgalle, at an elevation
of 5000 feet. With regard to var. |3, 1 am in some doubt whether it really belongs to this
species, notwithstanding that var. a, and a single colourless specimen of the normal form
given me by Mr. Cuming, seem to link it with the type. The only specimens I have
seen were in Mr. Cuming's collection, where they were erroneously referred to Palndomns
palustris, and none of the specimens contained opercula. In the absence, however, of
any adverse evidence, I provisionally regard this as a variety of P. nigricans.


P. nigricans has been collected by Mr. Gardner near Adams Peak, at an elevation of
6000 feet, by Mr. Thwaites in the Black Pool at Nuora Ellia (7000 feet), and by M.
Humbert* in the Paudel Oya Valley. The specimens quoted by Mr. Layard, from the
Balcadua Pass, do not belong to this species. Its range appears to be restricted to the
higher parts of the hills.


Shell ovate-conical, smooth (or decussate ?). Epidermis citrine ; shell ornamented with
two broad spiral bands of colour, with a narrow interspace on the periphery. Spire rather
small, acute, elevately conical. Whorls 5, the upper somewhat flattened, the last large,
somewhat cylindrical. Aperture ovate, pointed above, equal to f ths the height of the
shell. Peristome white. Operculum obliquely pyriform : nucleus small, spiral, close to
the outer margin, subbasal.

The only specimens I have seen of this shell are those in Mr. Cuming's collection,
which I take to be authentic, notwithstanding the absence of decussate sculpture ; and I
am unable to say how far, and in what direction, the form, &c., of the species varies. It
appears to be distinct, but it must be admitted that, seeing the great variability of most
of its congeners, it would be premature to separate it otherwise than provisionally until a
much larger series has been examined. PI. XXVII. figs. 6 & 10 represent one of
Mr. Cuming's specimens, and its operculum enlarged.

Genus PALUDOMUS, Swainson.

This genus, as restricted by the separation of Philopotamis and Tanalia, is character-
ized by the concentric structure of the adult operculum, and a spiral nucleus situated
about the middle of its height, and nearest to the left margin. The geographical range
of Paludomus is much greater than that of either Philopotamis or Tanalia, including not
only Ceylon, India, and Birma, but also extending in one direction to Egypt, Cape
Guardafui, the Mauritius, and the Seychelles, in the other to Java, Sumatra, and the
Island of Timor. It is remarkable, too, as contrasted with the above genera, that the
species have in some cases a very extensive range, following in this respect certain of the
low-country species of Melania, whose habit is similar, and that throughout the genus the
form and structure of the operculum are, so far as I have observed them, very constant.

The species of true Paludomus enumerated from Ceylon are pretty numerous, but a
careful comparison of the types in Mr. Cuming's cabinet, aided by those specimens which
I have myself collected, or examined in Major Skinner's and Mr. F. Layard' s collections,
has convinced me that they are all reducible to two species, viz.,

P. cMZinoides, Beeve.

P. Tanjoriensis^ (scil. Tanschauriensis), Gmelin.

* These specimens are stated by Dr. Brot (Cat. d. Melaniens) to be in part smooth, in part granulated, but identical
in form.

f I have taken the liberty of altering the orthography of this name to a form more in accordance with the modern
spelling of the place after which it is named.


PALUDOMtis CHILINOIDES, Reeve. (PI. XXVII. figs. 4 a-/.)

P. constrictus, Reeve ; P. phasianinus, Layard (not Reeve) ; P. lavis, Layard ; P. (Rivulma) Zeylanica,
Lea; P.fulguratus, Dohrn ; P. nasutus, Dohrn.

Shell thick, ovate or ovate-conic, smooth (rarely having traces of spiral sulci on the
upper part of the whorls). Colour of epidermis citrine or citrine yellow. Shell orna-
mented with spiral bands of brown crow's-feet markings, which sometimes coalesce into
transverse zigzags (P.fuhjumtus), sometimes, but very rarely, into longitudinal (spiral)
bands. Spire always exserted, sometimes elevated. Whorls 5, all rounded, obliquely
flattened above; upper whorls more or less eroded; last whorl ventricose. Sutures
impressed. Aperture ovate, flattened on the columellar side, angulate above. Outer lip
sharp : inner lip callous, usually white, rarely citrine-tinted on the edge. Interior of
aperture lined with white callus in old shells. Operculum with small spiral nucleus,
about central on the longitudinal axis, at about Jrd of the transverse axis from the
sinistral margin.

In the above description I have briefly indicated the chief points in which P. chili-
noides is variable. The most striking of these are the elevation of the spire and the
markings of the shell ; but the differences observable in the latter are not so great as to
lead to any doubt of the specific identity of the specimens in question. To illustrate the
variation of form I give a selected series, PI. XXVII. figs. 4 a-f, of which fig. 4 a is from
an unknown locality in Ceylon, figs. 4 6 and 4 c from Peradinia near Kandy, and the
remainder from a stream at Ballepane, on the Colombo and Kandy road. Prom these it
will be seen that, as in the case of Tanalia aculeate^ specimens from the same locality
vary somewhat in form, but in order to ascertain the full extent of variation a wider
selection is necessary. This series also exhibits a certain amount of variation in point of

Online LibraryAnthony HopeConchological miscellany (Volume 7) → online text (page 1 of 26)