Fossils from the Upper Mnsashino of Kazusa and Shimosa. 179 



293. Tjiitia vnlf/afula, Yokoyama. 

 PI. XVI r. Figs. 18, 19. 



A right and a left valve. 



The shell is closely related to the preceding in its general 

 shape. It is rather thin, moderately convex and obliquely ovate, 

 with all the margins rounded except the antero-dorsal wliich is 

 straight or somewhat excavated. The ears are small, especially 

 the anterior. lAinula short-lanceolate in outhne, deep, orna- 

 mented with a few longitudinal riblets. The surface is covered 

 with radiating ril)s which number about twenty-two and are flattish 

 and broader than, or about as broad as, the interspaces. The right 

 valve is 15.3 inillim. long, 18.5 milUm. high and 4.7 milhm. deep, 

 while the left is U. 1 millim. long, 15.9 millim. high and -i. 1 

 millim. deep. 



The distinctions of this species from the foregoing are the less 

 number of ribs, a somewhat flatter shell and the subangulate form 

 of the antero-ventral corner. 



Fossil occurrence. — Shito. 



Family Spondylidae. 



Genus Sttoitdylus, Linné. 



29». Spondylus crtieiitus, Lischke. 



PI. XIV. Fig. 24. 



Spondylus cnientus. Lischke, Jap. Meeresconch., I. p. 172, pi. XII, figs. 1-5. Dnnkev, 

 Ind. Moll., p. 24G. Pilsbry, Cat.', p. 143. 



A single upper valve of a young individual. It is irregularly 

 roundish, tolerably compressed and ornamented with distant 

 radiating ribs which are mostly crenate or granular near the 

 hinge-margin and foliaceous or spiny in the ventral. Between 

 these ribs there are also several interstitial riblets. The diameter 

 of the shell is a little greater than 12 millim. 



Living. — Central and Western Japan. 



