JOß Art.. 6.— M. Yokohama: 



distinction lying in the finer radiating ribs and closer, less prom- 

 inent, concentric laminae. 



Fossil occurrence. — Yokosuka Zone (Otsu). 



Family Saxicavidae. 



Genus Saacicara, Fleuriau de Bellevue. 



126. Saxicava orientalis, Yokoyama. 



Pl. VII. Figs. 2, 3. 



SI) ell thin, fragile, transversely elongato-oblong, moderately 

 convex, inequilateral, the anterior side being about one-third of 

 the posterior, rounded in front, subtruncate (?) behind, nearly 

 straight ventrally. Surface rather uneven, with an edge running 

 from beak to postero-ventral angle which is rather sharp near the 

 beak, but blunt and indistinct near the shell-margin. The 

 sculpture consists of coarse irregular lines of growth, most prom- 

 inent behind the umbonal edge. Palliai line indistinct, but 

 pearly lustre is visible along it. Tooth one in each valve, 

 triangular and transversely elongated, situated just below the beak 

 and close to it. 



A few specimens which we possess are all more or less 

 fractured. The left valve shown in the figure measures 11 millim. 

 in length, 7 millim. in height and 1,5 millim. in depth. 



A shell described as Saxicava ? fragilis Nyst. by Wood from 

 the Coralline Crag (vol. II, Bivalves p. 288, pl. XXIX, 6) is 

 somewhat like our species, though decidedly shorter. 



Fossil occurrence. — Yokosuka Zone (Otsu). Upper Musa- 

 shino of Kazusa. 



Family Pholadomyidae. 



Genus JP/#olaf/o#»ii/«, Sowerby. 



127. Pholadomya japonica, Yokoyama. 



Pl. VI. Figs. 30, 31. 



Two good specimens were obtained, but owing to the ex- 

 tremely fragile state of the shell, they became subsequently very 

 imperfect. 



