29 



glossy ; margin strongly denticulated. We found this 

 new species amongst sand from Falmouth harbour. Dia- 

 meter three quarters of an inch. Although this shell bears 

 some resemblance to the young Echinatum, it must not be 

 confounded ; the young of that species is always more 

 globose or convex ; the ribs are more sharp, and the 

 tvihercles more pointed and distant." Montagu. Dr. 

 Fleming is disposed to regard it as the young of C. 

 Muricatu m. 



* C. LiEVIGATUM. Pen. Br. Zo., vol. 4, pi. 51, fig. 40. 

 Mont. Test. Brit., vol. 1, p. 88. Fiem. Brit. An., p. 423. 

 On some parts of our coast, and especially at Hannafore, 

 apposite Looe Island, I find single valves thrown on shore 

 in abundance. 



C. FASCIATUM. Flem. Brit. An., p. 422. British 

 Museum, Obtained from near the Land's end. 

 HIATELLA. 



GENERIC CHARACTER: Shell with the valves equal, 

 the sides unequal, transverse, gaping at the anterior mar- 

 gin. Hinge with one small tooth on the right valve, and 

 two rather larger, on the left. Ligament external. 



* H. ARCTICA. Solen Minutus. Turt. Lin. Mont. Test. 



Brit., voL I, p, 53, pi. 1, fig. 4. H. A. Flem. Brit. An., 

 p. 4(51. Crouch's Intro, to Lam., pi. 8, fig. t>. Not 

 uncommon, burrowed in stone. 



H. .PRiECISA. My til us P. Mont. Test. Brit., vol. 1, 

 p. 165, pi. 4, fig. 2. Great confusion exists in the writings 

 of naturalists, concerning the two species of Hiatella 

 here given, and Saxicava Rugosa ; some supposing them 

 to be no more than one species, while by others they are 

 separated into different Genera. Under these circum- 

 stances, and having examined them when apparently 

 uninfluenced by foreign bodies, 1 have judged it best to 

 follow the opinion of Montagu, who considers them 

 distinct. H. Prascisa is common on rocks near low water 

 mark, attached to the roots of corrallines by the aid of 

 a bvssus, 



ISOCARDIA. 



GENERIC CHARACTER: The shell heartshaped, trans- 

 verse, gaping at the upper margin, the valves equal, the 

 beaks distant, diverging, spirally turned on one side ; two 

 flat, entering, cardinal teeth, one of them curved and 

 sunk under the beak; one elongated lateral tooth, situated 

 under the corselet. Ligament external, forked on one 

 side. 



I. COR. Chama Cor. Turt. Lin. Mont. Test. Brit. vol. 1, 

 p. 134. I. C. Flem. Brit. An. p. 418. Crouch's Intro, 

 pi. 8, fig. 7. Very rare. I have seen a specimen which, 



