MOLLUSCA. 
Mollusca at present considered as the type of the genus. In this 
~~’ shell, the valves gape at both extremities, the ligament is 
internal, and placed on a thick erect tooth in one valve, not 
inserted into the opposite side. As the M. vulsella of Lin- 
neus is close at both ends, and destitute of a tooth, it has 
been separated from the true myze, and formed into a dis- 
tinct genus by Lamark, under the title Vousrrua. This 
shell presented some difficulty to Linnzus, as he placed it 
at first among the Pinne, and afterwards among the Mye. 
Even Bruguiére gave it a place among the oysters. 
Another genus has been formed by Lamark from the mya 
siliqua of Chemn. (Conch.vol. xi. p. 192, tab. 198, fig. 1934). 
He calls it Gzycmmnris. Though nearly related to the true 
mye, by gaping at both extremities, yet it differs from them 
in the hinge, which is destitute of teeth, and in the Jigament 
being external. 
A new genus was formed by M. M. Groye, (Annales du 
Museum, vol. ix.), which he terms PANorEA, and assigns 
to it the following characters :—“ Coquille transverse, bail- 
lante inegalement au deux bouts, charniére semblable dans 
Yune et dans l’autre valve, ayant une callosité ou grosse dent 
allongée, placée en avant et surle corselet; decurrente sur 
le bord interieur, relevée en aréte, mousse et saillant poste~ 
rieurement; une dent cardinale conique um peu comprimée 
et arquée, et sur le valve droit une fosette dans laquelle s’en- 
eréne la dent de la valve opposée; ligament exterieur, cro- 
chets peu protuberans, corselet large, deux impressions 
musculaires dans chaque valve situées vers les extremites.” 
The type of this genus is the mya glycimeris of Gmelin first 
noticed by Aldrovandus. | It is inserted among the British 
shells by Mr. Donovan upon very slight authority. In the 
construction of the genus, we think, that M. Groye has acted 
properly, but there was no necessity surely for changing the 
trivial name (of the first described species) bestowed upon 
it by the discoverer. He has added another species from 
Monte Pulgnasco in Parma. In the trivial name of this 
species, we consider that he has been guilty of an act of 
injustice. He has called it P. Hayjas, in honour of Faujas 
St. Fond, the zealous Professor of Geology in the Museum 
of Natural History at Paris. But the truth is, that it was 
found by M. Cortezi, Counsellor at Parma, and a success- 
ful investigator of the organic remains of that district. It 
ought, therefore, to have obtained the name of P. Cortezi, 
in honour of the discoverer, instead of the name of Faujas. 
St. Fond, who received it from M. Cortezi, and whose sole 
merit in the subject consisted in his bringing it in safety 
to Paris. 
The principal error of Linnzus in the construction of this 
genus, consisted in the insertion of fluviatile shells among 
his marine species. Bruguiére readily perceived this error, 
and formed a new genus for their reception, which he called 
Unto. But this group, now denominated Nayapss by La- 
mark, includes the genera unio hyria, anadonta tridina, and, 
we may add, alasmodon. 
5. Soren.—This genus has undergone few changes since 
the days of Linnzus. The character has been somewhat 
restricted, and those species have been removed, in which 
the external margin is a little arcuated, and the cardinal 
teeth articulated, and two in number, and formed by Lamark 
into a new genus, which he terms SanecurvoLarra. The 
animals of this genus, according to Poli, differ from the so- 
lens, in haying the tubes of the syphon separate, and of 
unequal length and thickness. The S. minutus of Linnzus, 
found in our seas, is referred to the genus Hrarrrua by 
Cuvier, a genus very imperfectly defined, but-nearly allied 
to, if it be not identical with, the byssomia of the same au- 
thor, which includes the mytilus rugosus of Linnzeus. 
6. Trrima—This extensive genus of Linnzus, the es- 
sential character of which is to have an anterior inflection 
or fold in each valve, and lateral teeth, includes many shells 
341 
which differ greatly in form and. habit, and which disagree Mollusea. 
even with his own definition. 
provements have taken place in the distribution of the species. 
The first change in the genus of any consequence con- 
sisted in the separation of the fluviatile from the marine 
species. This was accomplished by Scopoli, (Introd. ad 
Hist. Nat. 397), who bestowed on them the generic name 
of Spherium. Bruguiére afterwards wantonly changed the 
name to Cycnas, and this change has been embraced by 
Lamark and other naturalists. 
Another new genus of fluviatile shells, allied to the pre- 
ceding, has been formed by Bruguiére and Lamark for the 
reception of one species. The genus is termed GaLATHEA, 
and the species G. radiata. There are two approaching 
hinge-teeth in the right valve; with a cavity in front, and 
two distant hinge-teeth in the left, with an intermediate 
large grooved callosity. The lateral teeth are of consider- 
able size. The ligament is external, and the muscular im- 
pressions are two in number, and lateral. 
The Tellina inequivalvis presents charactets which read- 
ily distinguish it from the other species with which Linnzeus 
placed it. The shell is inequivalve and inequilateral; the 
ligament is internal, and the lateral lamin are wanting. 
Besides, the animal differs from the other inhabitants of the 
tellin, and is nearly related to the solens. Hence Brugu- 
iére formed a new genus for its reception, which he termed 
PanpDora. 
There are several species of the genus tellina and Venus, 
which Bruguiére and Lamark have formed into a separate 
genus called Lucia, which is thus characterised:—“ Testa 
bivalvis, equivalvis, orbiculata, vel ovato transversa; nati- 
bus arcuatis, postice versis. Cardo dentibns cardinalibus 
1. s. 2. variabilibus ; lateralibus 1. s. 2. remotis, interdum 
subnullis.”. To this genus Lamark brings the Tedlina lactea 
and divaricata of Linneus, and the murieata of Chemn. 
(Conch. vol. xi. p. 209, tab. 199, fig. 1945-6), together with 
the Venus fimbriata, and Pensylvanica of Linnzus, and the 
Jamaicensis of Chemn. (Conch. vol. vii. p. 24, tab. 39, fig. 
408-9). Cuvier, however, has restored the T.lactea to the 
genus Loripes, which Poli instituted for its reception. 
7. Carprum.—This is, perhaps, the best constructed 
genus which Linneus formed. The characters are definite 
and obvious, and all the species are naturally allied. Hence 
few changes have taken place in their arrangement. The 
animal constitutes a new genus in the system of Poli, which 
he terms cerastis. 
Cuvier is disposed to constitute a new genus under the 
title Hemrcarpra, for the reception of the C. cardissa of 
Chemn., commonly called the Venus-heart cockle. The 
truncated appearance on the one side, and its being carin- 
ated in the middle, point out a conformation of the inhabi- 
tant different from the true cockles. Of this new genus we 
possess some fossil species. 
8. Macrra.—The ligament, in the marine bivalves, is, 
in general, placed on the outside, but in this genus, of which 
Lamark has formed his family macéreacea, the ligament 
is internal, and inserted in a cavity at the hinge formed for 
its reception. This family, as it stands at present, contains 
several well characterised genera. 
In the restricted genus, Macrra, as represented by the 
MM. stultorum of Linneus; the shell gapes a little, and the 
lateral teeth are strong, and lock into each other. The 
shells with age arrive at a considerable thickness. The in- 
habitant belongs to the genus callista in the system of Poli. 
The genus CrassaTELvA of Lamark contains shellswhich 
close exactly, and have the lateral teeth obsolete. He de- 
scribes seven fossil species, and eleven recent ones, viz. 
mactra glabrata, (Encyclopédie Méth. tab. 257. fig. 3); ve- 
nus divaricata of Martini, (Conch. vi. p. 318. tab. 30. fig. 
317, 318,) under the title Crassatella contraria ; and the 
Hence several important im- === 
