FISSURELLIDEA. 179 



B. Apex subcentral, perforation the shape of the shell ; ten- 

 tacles short, blunt. Genus Lucapinella, Pils. 



Genus FISSURELLIDEA s. str. 



Fissurellidea Orb., Voy. dans l'Amer. Merid., p. 447. Type, F. 

 megatrema Orh.=hiantula Lam., not of authors. 



The oblong shell is nearly covered by the mantle ; its edge is 

 thickened, rounded, with a white rim above. The fissure is very 

 large, subcentral in position. 



Animal much larger than the shell ; mantle thickened at its bor- 

 ders, much exceeding the foot in size. The latter bears a row of 

 epipodial papillae along its sides. Dentition unknown. 



But one species of the genus as here restricted is known. 



F. hiantula Lamarck. PI. 43, figs. 89, 90, 91, 92, 93. 



Shell oval, thin, depressed, nearly smooth, whitish, radiated with 

 purplish ; inside white ; margin thickened ; foramen oval, large, 

 (two-fifths the length of shell), broadly margined within. ( Orb.) 



Length 29, alt. 5 mill. 



Ensenada de Ros, on the coast of Patagonia, 15 leagues south of the 

 Rio Negro. 



Fissurella hiantula Lam., An. s. Vert, vi, pt. 2, p. 14, 1822. — 

 Fissurellidea hiantula H. & A. Ad. Gen. Rec. Moll, i, p. 449 (not 

 F. hiantula of Reeve, Sowerby, et al.). — Fissurellidea megatrema 

 Orb. Voy. dans l'Amer. Merid. p. 477, t. 63, f. 5-10.— Fissurella 

 aperta Sow., Reeve, Conch. Icon., f. 39. 



Animal, according to Orbigny, very large, fleshy, coriaceous, de- 

 pressed. Mantle very large, smooth above, strongly thickened at 

 the edges ; it encloses the shell almost completely. Foot not so large 

 as the mantle, oval, a little acuminated behind. Head very volu- 

 minous, with a very fleshy muzzle, the tentacles short, compressed, 

 obtuse, bearing the eyes at their bases. Between the foot and the 

 mantle there is a row of little papillae. The sole is of a blue color, 

 the rest yellowish. 



This is unquestionably the true hiantula of Lamarck, agreeing 

 with his description, and with the figure in Born's Test. Mus. Cses. 

 Vindob., p. 414, vignette fig. F. The shell identified as " hiantula" 

 by Reeve and others is quite a different form, having no resem- 



