J7 



one or two teeth, and a narrow pit for the internal liga- 

 ment. Ligament double; one external, short, the other 

 internal, fixed in the cardinal ptts. 



* A. COMPRESS UM. Mactra Listeri. Turt. Lin. Stew. 



Elera., vol. 2, p. 377. Venus Borealis. Pen. Brit. Zo., 

 vol. 4, p. 9G. Mactra C. Mont. Tost. Brit, vol. I, p. 96. 

 A. C. Flem. Brit. An., p. 432. On heaps of sand on the 

 banks of Looe river, and probably in other similar situ- 

 ations ; but scarcely abundant. 



* A. PRvETENUE. Mya P. Mont. Test. Brit., vol. 1, 



p. 41. A. P. Flem. Brit. An., p. 432. " It is not un- 

 commonly dredged from Falmouth harbour, but mostly 

 single valves." Montagu. I obtained a specimen with 

 the valves united. 



A. DISTORT UM. Mya D. Mont. Test. Brit., vol. 1, 

 p. 42. pi. 1, fig. 1. A. D. Fle,m. Brit. An., p. 432. " We 

 first noticed this species at Falmouth, amongst the sand 

 dredged from the harbour for manure, and have since 

 found it lodged in hard limestone at Plymouth, into which 

 it had bored like the Pholas ; probably the occasion of its 

 distorted growth." Montagu. I have found it not uncom- 

 mon in stones from deep water ; and ascribe the distorted 

 growth to its occupying holes not made by itself, and 

 which in time become too straight for it. Animals which 

 form their own habitations in the substance of the stone, 

 are commonly found to enlarge them according to their 

 growth; and maintain the most delicate structure of their 

 shells without injury. 



A, CONVEXUM. Turt. Lin. Flem. Br. An., p. 431, 

 Obtained from Mr. Peach at Gorran. 



Other species arranged by Fleming in this genus, will be 

 found in the genus Anatina. 



CQRBULEA. 



Valves of the shell unequal ; ligament interior. 

 CORBULA. 



GENERIC CHARACTER: The shell regular, valves 



unequal, as also the sides; closed or very slightly gaping. 



One large, conical, curved, ascending tooth in each valve, 



with a pit beside it; no lateral teeth. Ligament internal, 



inserted in the pits. 

 C. NUCLEUS. Mya Inequivalvis. Mont. Test. Brit., 



vol. 1, p. 38. C. Striata. Flem. Brit. An., p. 425. C. N. 



Quarterly Journal of Science, vol. 14, pi. 5, fig. 38. 



Montagu says, " this shell is by no means uncommon ; but 

 rarely to be obtained alive, or with connected valves; we 

 have found it on the coasts of Cornwall and Devonshire : and 

 in a living state dredged from Saicomb bay." I have obtiuaed 

 it from Gorran, d 



