360 SiPHONOFHOKA. MOLLUSCA. Venerid.e. 
Sub-class I. — SIPHONOPHORA. 
This great group is divided into two orders — I. 
or less separate — II. Piioladacea, in which the siphons 
Venekacea, in which the siphons are in general more 
are united. 
Order I. — VENERACEA. 
In this order the hinder margin of the mantle is fur- 
The sinus of the pallial impression is deep, oblique. 
nished with two more or less elongated siphons under 
triangular, and sharp-pointed. The surface of the 
the posterior adductor muscle, which are to a greater 
valves is usually concentrically grooved, and of a pale. 
or less degree separated from each other, and provided 
or even white colour. 
with a large fan-shaped muscle on each side, for the 
Genus Cytheuea {Meretrix). — This genus has a 
purpose of retracting them into the shell when the 
very solid, smooth, ventricose shell, of a more or less 
animal fears external danger. The gills are short, and 
transversely oblong, or ovate form, with three cardinal 
not produced into the canal of the siphon, and the foot 
teeth in the hinge in each valve, and a small conical 
is generally lamellar or elongate. 
anterior tooth beneath the nearly obsolete lunule. • The 
hinder lateral tooth is always lightly crenulated or 
Family — VENEKIDAD. 
striated, and the sinus of the pallial impression is 
moderate, and angular posteriorly. The surface of the 
valves is generally smooth and shining, and covered 
This family, with which we begin, is a numerous 
one, and is remarkable for the elegant forms and 
with a fulvous epidermis. 
varied colours of the shells of many of the species 
Genus Cuneus {Meroe). — This genus is remarkable 
which belong to it. The animals have a large, com- 
for the compressed, ovate-trigonal shell, having the area 
pressed, tongue-shaped foot, by means of which they 
of the lunule deeply excavated, and the margins of the 
crawl ; and short unequal siphons, united sometimes 
shell regularly toothed. 
for a considerable portion of their length. The shell 
Genus Trigona. — T his genus has a triangular. 
is regular, closed, or sometimes slightly gaping ; gene- 
wedge-shaped shell, with very prominent beaks, and 
rally free, seldom burrowing ; suborbicular in shape 
an indistinct lunule. The hinge is provided with three 
or oblong. The hinge has usually three diverging 
and sometimes four cardinal teeth, and a small anterior 
cardinal teeth in each valve, and the hinder lateral 
one. The hinder lateral tooth is torn and divided ; the 
tooth, when present, is compressed, and forms a part 
internal margin of the valves is entire, and the pallial 
of the margin of the shell; the ligament is external. 
sinus rounded, short, and horizontal. The shells are 
marginal. The muscular impressions are smooth and 
usually thin and gibbous, and are frequently covered 
polished, and the pallial line is sinuated. The animals 
with a glassy-looking epidermis. 
of this family are all marine, free, and possess con- 
Genus Dione. — T his genus, as represented in Plate 
siderable locomotive powers ; a few only burrowing in. 
10, fig. 1, by Dione Chione, has an ovate, transverse. 
or perforating rocks. They are found in all parts of 
ineipnlateral shell, with the interior margins of the 
the world, though there is not much known of their 
valves often thickened. The hinge has three cardinal 
habits. Some of them, liowever, are eaten by man in 
teeth in each valve, and a small anterior tooth under 
different parts of the world, and are even esteemed a 
the lunule. The hinder lateral tooth is simple, neither 
delicacy. Their taste, we are told, is stronger than that 
torn nor striated ; and the pallia! sinus is wide, deep. 
of oysters, and one must be habituated to it, to relish it. 
and somewhat ovate. The shells are often inflated. 
The Venus shell appears to have been held in honour 
and their surface is either smooth, sulcated, striated, or 
by the ancients, and dedicated to the Goddess of Love. 
lamellar. 
The shells of the Venericlce show little organic structure. 
Genus Circe. — T his genus has an ovate, somewhat 
and their texture is very hard, approaching the por- 
triangular, solid shell, depressed at the beaks. The 
cellanous univalves in density, and in the absence of 
hinge has three cardinal teeth in each valve, and there 
almost any trace of animal matter. The species are 
is scarcely any trace of a pallial sinus. The external 
very numerous, upwards of five hundred and fifty being 
surface of the valves is smooth, or concentrically striated 
indicated or described in M. Deshayes’ Catalogue of 
or grooved. 
the Venaridm in the British Museum. They differ 
Genus Venus. — T his genus, as now restricted, has 
amongst themselves considerably in form, number, and 
a thick, turgid, ovate shell, with a prominent ligament, 
structure of the teeth, the shape of the pallial irapres- 
a distinct lunule, and a small, often oblique pallial 
sion, &c., so that for convenience sake they have been 
sinus. The hinge is thick, and possesses three teeth 
formed into no fewer than sixteen genera. We will 
in each valve, which are divaricate, and sometimes 
only mention a few. 
bifid. The surface of the shell in this genus is either 
Genus Artemis. — T his genus has an orbicular. 
warty, or ornamented with concentric ribs or striae or 
compressed shell, deeply lunulate under the beaks, and 
lamellae, or they are decussated by longitudinal furrows. 
the hinge is provided with three teeth in each valve. 
Genus Mercenaria. — T his genus has a triangu- 
