GASTEROPODA PECTINIBRANCHIATA. 
361 
Nerita, Lam. {Peloronta, Oken), has no umbilicus. Their shell is thick, the columella toothed, the operculum 
calcareous. The eyes of the animal are supported on pedicles at the sides of the tentacula; and the foot is mode- 
rate in size. There is but slight reason to distinguish among them the Velates, Montf., where the side of the 
columella is covered with a thick, swollen, calcareous layer ; and the Neritina, Lam., in which the columella is 
toothless, and the animals are inhabitants of fresh waters. Some have, however, a delicately toothed columella, 
and among these is one whose spire is armed with long spines, (Clitho, Montf.). [The species of Neritae are very 
numerous. M. Lesson has brought one from Australia, where it lives abundantly upon trees ! This fact ought 
to make us more than ever wary of separating the marine from the fluviatile species. Indeed, some real Neritinae 
can live both in fresh and salt water, and others are altogether marine.] 
Recent observations induce us to arrange near to the Trochoides 
THE SECOND FAMILY OF THE PECTINIBRANCHIATA,— 
The Capuloides,* — 
Which comprises five genera, four of which are dismembered from Patella. All of them have a wddely 
open shell, scarcely turbinate, without an operculum, or emargination or canal. The animal is male and 
female, and resembles the other Pectinibranchiata. Their branchial comb is single, laid across the vault 
of the cavity, and its filaments are often very long. 
Capulus, Mont. {Pileopsis, Lam.) — 
Have a conical shell, with the summit recurved a little in spiral, whence they were for long placed with 
the Patellae. The branchiae are in a series under the anterior margin of their cavity ; the proboscis is of 
considerable length ; under the neck is a much plaited membranous veil ; there are two conical tentacula 
with the eyes at their base on the outside. 
Hipponyx, Defr., appear from their shell to be fossil Capuli, but are very remarkable for the base of calcareous 
layers on which they rest, and which has probably been excreted by the foot of the animal. [Hipponyx is a truly 
bivalve shell.] 
Crepidula, Lam. 
Shell oval [variable], with an obtuse point obliquely inclined backwards towards the margin : the 
under-side is generally concave, and the inner lip forms a broad, flattish, sharp-edged, toothless, hori- 
zontal plate, which about half covers the aperture. The abdominal sac containing the viscera is upon 
this plate, the foot under it, the head and the branchiae in front. The branchiae consist of a series of 
long filaments attached under the anterior margin of the branchial cavity. Two conical tentacula bear 
the eyes at their exterior bases. 
Pileolus, Sowerby, seem to be Crepidulae, of which the transverse plate occupies half of the aperture, but their 
shell has a greater resemblance to Patella. The few species known are fossil. 
Septaria, Ferus. {Navicella, Lam.), resemble the Crepidula, excepting that their summit is symmetrical, and 
turned down on the posterior margin, and their horizontal plate projects less. The animal has, moreover, a tes- 
taceous plate of an irregular shape, attached horizontally upon the superior surface of the muscular disk of the 
foot, and covered by the abdominal sac, which rests in part above. It is, probably, the analogue of an operculum* 
but does not fulfil its office, being in some degree internal. The animal has long tentacula, and at their outside 
are peduncles to support the eyes. They live in the rivers of warm countries. 
Calyptr^a, Lam. 
Shell conoid, the cavity furnished with a lateral internal appendage, very variable in form, which is 
as it were the beginning of a columella, and is interposed in a fold of the abdominal sac. The branchiae 
are composed of a range of numerous hair-like filaments. Some have the appendage adhering to the 
bottom of the cone, folded itself into a cone, or tube, and descending vertically. Others have it placed 
almost horizontally, adhering to the sides of the cone, which is marked above with a spiral line, that 
gives to their shell some relation to that of the Trochus.f 
SiphonariaJ, Sowerby. 
Dismembered from Patella, to which in general form and appearance it very nearly approaches, but 
its margin is a little more prominent on the right side, and it is hollowed underneath with a shallow 
groove which opens at this prominence, and with which a lateral hole in the cloak corresponds, to intro- 
* M. de B .ainville inserts the most of them among \\\& Paracephala- 
phora hermaphrodita, Fam. Calyptracea, but they seem to me to be all 
dioicous. [It is necessary to arrange with them the Lnttia of Gray, 
which has a shell almost identical with that of Patella, but the animal 
is pectinibranchous. We have at least one native species, (Puf. Cle- 
landi ) .] 
+ [Mr. Broderip has described many species in the 1st vol. of the 
Trans, of the Zoo! . Society, accompanied with beautiful figures ; and 
Mr. Owen has given an excellent anatomy of the genus in the same 
work.] 
t Apparently the same as the Gadinia of Gray.— Phil. Mag. April, 
1824. 
