MOLLUSCA. 
previously restricting the character of the original as fol- Mollusca. 
lows: “ Testa bivalvis zequivalvis, binzequilatera transversa === 
342 
Mollusea. following new species, rostrata, Kingicola (from King’s Is- 
Ss land!) donacina, suleata, subradiata, erycinea, cycladea, 
and strata. 
The genus Erycrna is composed entirely of fossil species. 
Lamark has assigned it the following character: “ Testa 
bivalvis, equivalvis, inequilatera, transversa. Dentes car- 
dinales bini, superne divergentes, cum foyeola minima in- 
termedia: laterales compressi oblongi. Ligamentum fove- 
ola cardinali insertum.” From the situation of the ligament 
being inserted in the small space between the teeth, the pit 
or cavity is less than in any of the other genera. The mus- 
cular impressions are two in number. 
The transverse mactre, which gape, but are destitute of 
lateral teeth, such as the M. lutraria of Linnzeus, compose 
the genus Lurrarza of Lamark. The species already men- 
tioned, and the mya oblonga of Gmelin, or mactra hians of 
Montagu, occur on our coasts; the former in great abund- 
ance at the mouths of the European rivers. 
The genus Uneunrna, formed by Daudin, contains only 
one species, existing in the cabinet of Favanne. It is un- 
certain from what country it came. It is a regular longi- 
tudinal shell. The hinge is formed by one small tooth be- 
tween two oblique pits. The muscular impressions are two 
in number. It is figured in Deterville’s edition of Buffon. 
(Hist. Nat. des Coquil. tom. xx. f. 2, 3.) 
Another genus established by the same author, and termed 
Eropona, is subtransverse, irregular, and gaping, the hinge, 
in one valve, consisting of one hollowed tooth, and in the 
other a depression between two eminences. It includes 
two shells from the cabinet of Favanne. It is intermediate 
between the mactre and mye. 
9. Donax. The shells of this genus are readily known 
at first sight by their singular cuneiform shape. The hinge 
teeth are two in number, and the lateral teeth are spread- 
ing. The ligament is external, and, like the telline, it is 
placed on the shortest side. This is a circumstance of rare 
occurrence among the inequivalve testacea. The animal 
belongs to the genus peronzea of Poli. 
Lamark has instituted a genus nearly allied to the pre- 
ceding, termed Perrrcoxa, the shells of which gape alittle 
at both ends. There is one hinge tooth in one valve, and 
a bifid one in the other. The ligament is external; the 
muscular impressions are two in number ; the structure of 
the hinge teeth, and the absence of the lateral teeth, at once 
distinguish this genus from the denax and venus. These 
animals are likewise peculiar in their habits. Lamark quotes 
the venus lithophaga of Retzius, Act. Acad. Tour. vol. iii. 
p- 11, and the venus lapicida of Chemn. Conch. x. p. 356. 
tab. 172, f. 1664-5. But Lamark’s genus has been again 
altered by Fleurieu-Bellevue, who has formed his genus 
Rupetxarta, from the V. lithophagus of Retzius, and an- 
other species termed striata. (Mem. de Acad. de la Ro- 
chelle, ii. tab. 2, fig. 9.) In this genus the shell is transverse 
and inequilateral, compressed in the anterior part, and 
swollen behind. There are two crooked hinge teeth on 
each valve, one simple, the other bifid. The ligament is 
external, and there are two muscular impressions. The 
donax irio belongs to this genus. The same author has 
formed two other genera of borers. The first he terms Ru- 
PICOLA, having a transverse inequilateral shell, a little gap- 
ing at the ends: no teeth or callosities. In an internal 
projection of each valve, there is a pit for the ligament. 
The other genus is named Saxicava. It is transverse, 
inequilateral, and gaping, without teeth or callosity, or pit. 
The ligament is external. 
10. Venus. This Linnean genus contains so many 
species, that there is considerable difficulty in studying it. 
The formation of new genera, from its members, by dimi- 
nishing their numbers, must prove highly acceptible to the 
student of conchology. Lamark has succeeded so far by 
vel suborbicularis. Dentes cardinales tres in utroque val- 
va, ad nates basi convergentibus. Ligamentum externum, 
nymphas labiaque obtegens.” The three diverging hinge 
teeth constitute the essential character of the genus, so that 
Lamark has been able to form three other genera from dif- 
ferent characters. 
The genus CyrHerea (the meretrix of Lamark’s Sys- 
téme des Animauz) is thus characterised: ‘“ Cardo dentibus 
duobus tribusve approximatis, basi convergentes ; uno soli- 
tareo remotiuscula sub ano.” It must be confessed that the 
insulated teeth under the lunule, in the absence of other 
characters, is obviously artificial. This genus contains 
many species requiring subdivision. 
The genus VENERICARDIA, formed for the reception 
of some fossil species, is thus defined: “Testa bivalvis, 
aquivalvis, inaquilatera, extuslongitudinaliter costata. Den- 
tes cordinales sub-bini crassi obliqué secundi.” The num- 
ber of hinge teeth, and the longitudinal ribs, readily distin- 
guish it from the genus Venus. It is very limited in recent 
species. 
Another genus instituted by Lamark, and termed by him 
Capsa, has two teeth in one valve, and a bifid tooth in the 
other, the type of which he considered to be the donax lavi- 
gata of Gmelin. 
It was in the construction of the characters of the genus 
Venus that Linnzeus unfortunately indulged in obscene al- 
lusions. It is now time that the pages of natural history 
were freed from such pollution. Other names, more ex- 
pressive, can easily be substituted, alike advantageous to 
the interests of science, and the reputation of the illustrious 
Swede. 
11. Sponpyxvus.—The shells which Linnezus included 
under this head are usually denominated prickly oysters. 
The genus represented by the S. gederopus of Linnzeus. 
The S. plicatula of the same author has been separated 
from the spondyli, and placed in a new genus, under the 
name PrrcatuLta. This genus differs from the former in 
the valves wanting ears, and in the absence of the triangu- 
lar unisulcated space at the teeth of the under valve, so 
characteristic of the parent genus. 
12. Cuama.—This is by no means a well constituted 
genus in the Linnzan system, as it includes shells possess- 
ing very different characters. It has, accordingly, under- 
gone several important alterations. Bruguiére proceeded 
so far by establishing two new genera, and Lamark, follow- 
ing the same plan, has added three more to the number. 
Those shells, which now belong to the genus Cuama, are 
irregular, inequivalve, and adhere to other bodies. The 
hinge contains only one thick oblique tooth. It is repre- 
sented by the chama Lazarus of Linnzus. 
The genus Carpita, of Bruguiére, represented by the 
C. variegata, (Lister, tab. 344, fig. 84.,) consists of equivalve 
free shells, with the hinge furnished with two unequal teeth, 
the one situated under the beak, the other lateral, under 
the anterior margin. 
The chama cor of Linnzus appeared to Lamark possess- 
ed of sufficient characters to constitute a distinct genus, 
which he has named Isocarpra. It is an equivalve, free, 
regular, heart-shaped shell, with two cardinal teeth, and a 
separate lateral one, with separate, diverging, involuted 
beaks. It is an inhabitant of the British Seas. 
To Bruguiére we owe the institution of the genus Tri- 
pacna, which is represented by the chama gigas of Lin- 
neeus, the largest shell in nature. The shell is equivalve 
and free. The hinge consists of two compressed teeth, and 
there is a gape at the lunule. 
From the preceding genus of Bruguiére, Lamark has se- 
parated the chama hippopus of Linnzus, and formed from 
