FISSURELLA. 177 



but specimens of a white or crimson color occur, still having, how- 

 ever, the short white flames around the orifice. The sculpture 

 consists of numerous radiating riblets separated by narrow grooves; 

 these riblets being smaller in front. Inside white, with a red line 

 bounding the perforation-callus ; edge crenulated. 

 Length 20, breadth 17, alt. 5 mill. 



Cape Lookout to Barbados. 



F. pustula Lamarck, An. s. Vert, vi, 2d pt., p. 14, 1822 ; and of 

 subsequent authors. — Not Patella pustula Linn., Syst. x, p. 784. an 

 unrecognizable species of Glyphis. 



A well-known species, inhabiting Cuba, St. Thomas, St. Croix and 

 the West Indies generally, recently reported by Dall from the 

 region of Hatteras. It is readily seperable from F. fascicularis by 

 the more anterior position of the orifice, and the shorter shell, ob- 

 viously truncated in front. 



F. fascicularis Lamarck. PI. 37, figs. 59, 60 ; pi. 59, figs. 48, 49, 



50. 



Shell oval, depressed, not truncated in front ; margin sinuous, 

 elevated in front and behind ; orifice cross-shaped, separated from the 

 front margin of the shell by double its own length or more. 



This shell has the same saddle shape as the preceding, but is less 

 truncated in front. The radiating riblets (usually about 47 in num- 

 ber) are coarser ; they are slightly cut by concentric stria?. The 

 color is usually crimson-red, the interstices whitish ; darker rays 

 when present, not conspicuous. Inside white or tinged with pink, 

 the perforation-callus sometimes bordered by a red line. Edge cren- 

 ulated. Length 30, width 22, alt. 6-8 mill. 



Florida Keys to Porto Pico and Jamaica. 



F. fascicularis Lam. An. s. Vert, vi, 2d pt., p. 14. — Reeve, Conch. 

 Icon., f. 59. — Arango, Fauna Mai. Cubana p. 228. — Sowb. Thes., 

 iii, p. 204, f. 212-214. — Clypidella fascicularis Lam., Dall, Prelim. 

 Cat. Moll. S-E. U. S. p. 173. 



More oval than F. pustida, and having the fissure nearer the cen- 

 ter. 



Dall (I. c.) places this species in Clypidella, but separates F. pus- 

 tida under Fissurellidea. F. pustula is, however, the type of Clypi- 

 della ! 



12 



