25 
The Conch® are divided into Fluviatiles and Marin®. 
CONCUR EL U VIA TIL ES. 
The shells covered with a false epidermis, and having two 
lateral teeth near the hinge. 
CYCLAS. 
GENERIC CHARACTER: Shell ovate, globose, trans- 
verse; equalvalved, the beaks tumid; cardinal teeth very 
small, sometimes scarcely perceptible ; occasionally two 
each valve, one of them plaited in two; sometimes only 
°ne plaited or lobed tooth in one valve, and two in the 
other ; lateral teeth transversely elongated, compressed, la- 
mellar. Ligament external. Mr. Gray’s character ot his 
Gyclad® is, the shell subcordate, porcellaneous, thin, 
covered with a hard, olive, horny periostraca ; hinge teeth 
two or three, diverging; lateral teeth distinct, laminar. 
C - CORNEA. Tellina Cornea. Turt. Lin. Pen. Brit. 
Zo., vol. 4, pi. 49, fig- 33. Cardium C. Mont. Test. 
Brit., vol. 1, p. 86. C. C. Flem. Brit. An., p. 452. 
Gray’s Turton’s Manual of land and fresh water shells, 
P. 280, pi. 1, fig. 2. There are few situations in Cornwall, 
in which the Cyclad® can find a proper habitation ; anti 
hence the present species is in a great measure local. I 
have obtained it, by favour of a Lady, from near Helston. 
PISIDIUM. 
GENERIC CHARACTER: The shell suboval, wedge- 
b shaped, unequal sided ; the teeth as in Cyclas. 
^•AMNICLM. Cardium A. Mont. Test. Brit., vol. 1, 
P. 86. Cyclas A. Flem. Brit. An., p. 453. P. A. 
Gray’s Turt., p. 285, pi. 1, fig. 5. In the Swanpool, near 
Falmouth. 
CONCIIJE MARIN JE. 
. Generally with no lateral teeth : sometimes the whole 
S * e h, except the beaks, covered with epidermis. 
CYPRINA. 
GENERIC CHARACTER : The valves equal, the shell 
°hliquely heartshaped, the beaks obliquely curved. Three 
nnequal cardinal teeth, approaching at their base, slightly 
‘‘‘verging above. One lateral tooth, distant from the binge, 
the anterior side, sometimes obsolete. Callosities ot the 
^ytnphag large, arched, ending near the beaks by a pit. 
ligament external, partly sunk under the beaks. 
By having an epidermis, and their sometimes almost 
J’hsolete lateral tooth, the Cyprin® are somewhat allied to 
m fresh water Conch®. 
G- ISLANDICA. Venus I. Turt. Lin. V. Mercenaria 
Ben- Brit. Zo., vol. 4, pi. 53, fig. 47. V. I. Mont. Test. 
