CEPHALOPODA FEOM THE HOKlvAIDÔ. 11 



HELICOCERAS (?) VENUSTÜM m. 

 ri. III., fig. 4; pi. v., iigs. 1 and 2. 



VJO'2. IlamUcs vcnustus Yabe : the Li.st of Aniinoiiites from 

 the Cretaceous of the Hokkaido, in Outlines of the 

 Geology of Japan : ])escriptive Text to accompany the 

 Geological Map of the Empire. 



Shell sinistral, forming a helicoid spiral of a very wide coil. 

 AYliorls slender, very slowly increasing in diameter toward the 

 anterior end ; subcircular in cross-section when young, transversely 

 oblong in the aged specimens. Surfece with numerous transverse 

 stricC and periodic ribs, the latter hardly distinguishable from 

 the former on the umbilical side, but becoming gradually higher 

 toward the external side, until they are most elevated on the 

 upper side, each being here furnished with two tubercles. In- 

 tercalated striœ numerous, simple, smooth and uniform, becoming- 

 somewhat feebler on the umbilical surface ; their intervals vary 

 from 1.0 mm. to O.o mm. Both striae and periodic ribs maintain 

 a slightly oblique course. 



The suture line is only partly visible. It is apparently very 

 similar to that of the preceding species, being divided into three 

 bifid saddles and a corresponding number of similarly bifid lobes 

 on either side of the siphonal line. These saddles and lobes are 

 nearly uniform in size and are moderately incised. The external 

 lobe is somewhat shallower than the others. The siphon is on 

 the median line of the external surface of the whorl. 



There are two specimens of this pretty species in the writer's 

 collection, one of which is from lower part of the Tachyducus- 

 beds, exposed along a right triljutury of the Saushi-sanushibe. 



