6 ART. 20. — M. YOKOYAMA. 



figs. 1-4). But our species lias a larger umbilicus and closer 

 ribs. 



Locality : — Kaizara, in a dark micaceous shale. 



3. PEMSPHINCÏES (BIPLICES) KAIZARANUS m. 



PL I. Fig. 4. 



The compressed, discoidal shell shows a wide umbilicus which 

 is slightly deepened. The whorls are a little less than one-half 

 involute, ovate in section, somewhat higher than broad and 

 ornamented with numerous, elevated but obtuse, rigid, radial ribs 

 separated by interspaces of a like breadth. These ribs which 

 number about 50 on the last whorl generally split into two a 

 little higher than the middle of their lengths, but occasionally 

 there is a simple rib between. There are also two deep grooves 

 in the last whorl, the one near the mouth and directed obliquely 

 forward, and the other diametrically opposite the first one and 

 directed radially. In the inner whorls too such grooves seem 

 to have been present, as the third is seen diametrically opposite 

 the second. The suture-line is unknown. 



We have only a single specimen of this species which shows 

 the following dimensions : 



Diameter of shell oo mm. 



Umbilical width 0,-34 



Thickness of whorl 0/20 



Height above umbilical suture 0,33 



Our fossil shows many relations to Perisphinctes subcolubrinus 

 Waagen (Jurassic Fauna of Kalch, p. 180, pi. ALIA., fig. 3), 

 an Oxford species found in India, Poland and Portugal. But 



