8 ART. 20. M. YOKOYAMA. 



o. PERISPHINCTES (ATAXIOCERAS) sp. 



PL I. Fig. 6. 



A single specimen from Kaizara, not quite perfect, shows a 

 flat cliscoidal shell with a wide umbilicus and numerous volutions 

 which are about I involute. The whorls are oval in transverse 

 section, slightly higher than broad, with convex lateral sides and 

 steep umbilical wall. The transverse ribs which rise at the 

 umbilical suture number about 34 in the last whorl, and are 

 nearly radial in the same whorl, while in the inner ones they 

 are directed obliquely forward. These ribs are more or less rigid 

 and sharp, and split into two at half their length or a little more. 



The diameter of the shell measures 40 mm. and that of the 

 umbilicus 19 mm. 



Our species much resembles Perisphi?ictes occultefurcatus 

 Waagen from Katch (Jurassic Fauna of Kateh, p. 195, pi. XL., 

 fig. 4). But as the venter in our specimen is not well preserved 

 it is not possible to determine whether there is a shallow dorsal 

 groove as in the Indian species. Moreover the ribs are somewhat 

 loss in ours. 



0. OPPELIA ECHIZENICA m. 



PI. I. Fig. 7. 



A single specimen of a strongly compressed, discoidal, keeled 

 shell, about 31 mm. in diameter with an umbilical width of about 

 12 mm. The whorls are laterally compressed and only slightly 

 convex, apparently without any ribs, the only ornamentation being 

 a row of distant nodes which bounds the keel on both sides and 



