FISSURELLA. 175 



Orifice round, subcentral, margin slightly, irregularly wrinkled. 

 Differs from its congeners chiefly in the rotundity of its orifice. 



(Sowb.) Length 50, width 40, alt. 22 mill, 



Habitat unknown. 



F. melvilli Sowb. P. Z. S. 1882, p. 120, t. 5, f. 11. 



Subgenus Fissuridea Swainson, 1840. 



Fissuridea Swains. Malacology, p. 356. Type jP. pileus Sw.=.F. 

 pileopsoides Rve.==F 1 . galeata Helb. 



The apex leans forward over the anterior end of the shell, in this 

 section. The perforation is small, oval, opening forward rather 

 than upward. The callus surrounding the hole inside is oval, with 

 entire, not very distinct edges. Outer surface having radiating 

 riblets, and fine concentric striae. 



Animal not observed. 



F. galeata Helbling. PL 60, figs. 66, 67, 68. 



Shell oval, elevated, the apex projecting anteriorly as far as or 

 over the margin. Perforation small, oval, directed forward. Sur- 

 face with radiating riblets decussated by finer concentric strise. 

 color white. Length 17, breadth 10J, alt. 8 mill. 



Isl. of Masbate, Philippines. 



Patella galeata Helbling, Beitrage zur Kenntniss neuer und 

 seltener Conchylien, in Abhandl. einer Privatgesellschaft in Bohmen 

 zur Aufnahme der Mathematik, der vaterlandischen Geschichte und 

 der Naturgeschichte, Bd. iv, p. 103, t. 1, f. 3, 4, 1779.— Von Mar- 

 tens, in Malak. Blatter, xvi, p. 235. — F. pileopsoides Rve. Conch. 

 Icon., f. 99, 1850. — F. pileopsides (sic.) Sowb. Thes. Conch, iii, p. 

 199, f. 120, 121.— F. pileus Swains. Malacol., p. 356 (teste H. & A. 

 Ads.), not described. 



A curious shell, having the summit hooked over the front margin. 

 Since there is some doubt about which of the two names -pileop- 

 soides or pileus, should be used, it is certainly best to revert to the 

 ancient one proposed by Helbling. 



Subgenus Clypidella Swainson, 1840. 



Clypidella Sw., Malacol. p. 356. Type, F. pustula, (Sowerby's 

 Genera, Fissurella, fig. 3.). — Clypidella, in part, of authors. 



The shell is short-oval, depressed, saddle-shaped, the two extremi- 

 ties elevated so that when standing on a plane the side margins 



