43 



orbicular, subirregular, nearly flat, slightly convex above, 

 with a small apes near the middle ; margin acute ; inner 

 surface rather concave, with a callous disk, depressed in the 

 centre, with a smooth border) all the recognized species of 

 which are Indian. 



CALYP TRICIANA. 



Shell always external, covering the animal. 

 EMARGINULA. 

 GENERIC CHARACTER: Shell shieldlike, conical, 

 vertex inclined, cavity simple, the hinder margin notched. 



* E. FISSURA. Patella F. Turt. Lin. Pen. Brit. Zo., 



vol. 4, pi. 90, erroneously marked 151. Mont. Test. 

 Brit., vol. 1, p. 490, E. F. Flero. Brit. An,, p. 365. 

 Not uncommon, from deep water. 



FISSURELLA. 

 GENERIC CHARACTER: Shell shield-like or depressed 

 conical, concave below ; without a spire, and perforated 

 at the top; aperture oblong. 



* F. GR^ECA. Patella G. Turt. Lin. Pen. Brit. Zo., 



vol. 4, pi. 89, fig. 153, Mont. Test. Brit., vol. 2. p. 492. 

 F. G. Flem. Brit. An., p. 364. Rare. I have obtained it 

 from near Looe, at Falmouth, and near the Land's-end but 

 not with the animal. Mr. Forbes (Fauna Monensis) says 

 that their habit is, to attach themselves to Pectens, in 

 deep-water. 

 F. APERTURA. Patella Fissurella. Turt. Lin. P. 

 Apertura Mont. Test. Brit., vol. 2, p. 492, pi. 13, fig. 10. 

 Flem. Brit. An., p. 364. Very rare. 



* F. NUBECULA. Flem. Brit. An., p. 365, from Dr. 

 Turton; who obtained it near the Land's-end ; from whence 

 also I procured a few specimens. It has been found at 

 Gorran by Mr. Peach. 



PILEOPSIS. 

 GENERIC CHARACTER: Shell obliquely conical, cur- 

 ved forward; the top bent, approaching to a spiral; 

 aperture somewhat oval; anterior margin shortest, acute, 

 ending in a slight sinus ; hinder margin larger, round ; a 

 lengthened, arched, transverse muscular impression under 

 the hinder border. 



* P. HUNGARICUS. Patella H. Turt. Lin. Pen. Brit. 

 Zo., vol. 4, pi. 90, fig. 147. Borlase's Nat. Hist. Corn., 

 pi. 28, fig. 4. P. Ungarica. Mont. Test. Brit., vol. 2, 

 p. 486. Capulus H. Flem. Brit. An., p. 363. Not un- 

 common on the Pinna from deep water; and one specimen 

 of unusual size had its border so curved to accommodate 

 itself to the irregularity of the surface, as to show that k 



