1901.] NATURAL SCIENCES OF rillLADELPIIIA. 205 



throughout, the posterior end sometimes a little produced. Sculp- 

 ture of slightly irregular radial riblets about ef[ual to their inter- 

 vals, often stronger posteriorly, gradually weakening anteriorly 

 and \vholIy obsolete on the anterior half or third of the valve; 

 rude, crowded, bluntly lamellar circular striae everywhere minutely 

 rougrhening the surface. Interior white, the pallial sinus large 

 and rounded, extending to about the middle of the shell's length. 

 Hinge rather strong, the right valve with two diverging, rather 

 compressed, and long, erect, cardinal teeth, the posterior one the 

 more slender; left valve with an erect, triangular, bilobed cardinal, 

 with a subobsolete, diverging tooth on either side. Ligament 

 short, almost entirely immersed. 



Length 15, alt, 15, diam. 12 mm. 



Hirado, Hizen (Mr. Y. Hirase). Types No. 80,580, coll. 

 A. N. S. P., from No. 1,199 of Mr. Hirase's collection. 



A very short, subglobular species, somewhat related to P. lith- 

 ophaga Retz. of Europe, but rounder, with more deeply immersed 

 ligament, stouter hinge, different shaped and stronger teeth. The 

 sculpture in some specimens is not dissimilar. As usual in the 

 genus, the teeth are liable to fracture, and when broken often do 

 not show plainly that they are injui-ed. 



In a variety which may be called var. sculpturata the posterior 

 end is more prolonged, and the entire surface of the valves ribbed. 

 The teeth agree with P. eyelus. Types from Puttalam, Ceylon 

 (Coll, A, N. S. P.). One specimen from Hirado, Hizen, seems 

 to belong here. 



Petricola cyclus belongs to the section Rupellaria,* as defined 

 by Prof. Dall in his exposition of the Pelrlcolidce ; " the section 

 Clandiconcha being represented in Japan by P. monstrosa, and the 

 section Petricolaria by P. ceqiiistriata Sowb. 



VENERID.E. 

 Venus Hirasei n. sp. 



Shell rounded -oval, ventricose, inequilateral, very solid and 

 strong; cream-white, clouded and maculate with dull brown. Sur- 

 face lustreless, sculptured with 24 to 28 strong, curved, radial 



*Fleurieu-Bellevu, Journ. de Phys., LIV, 1802, p. 345; Bidl. Soc. 

 Philomath, de Paris, III, 1802, p. 106. 



* Trans. Wagner Free Institute of Science, III. Pt. 5 i December 1, 1900), 

 p. 1058. 



