CEPHALOPODA FKOM THE HOKKAIDO. 



19 



SUBGROUP OF GAUDRYCERAS TENUILIRATUM. 



GAUDRYCERAS TENUILIRATUM m. 



PI. III., figs. 3 and 4. 



1890. Lyioceras Sacya Yokoyama : Versteinerungen îuis der 

 japanischen Kreide. P. 178, PI XVIII. figs. 12 

 a, b, 13 a, b. 

 1894. Lytoceras Sacya Jimbö : Beiträge zur Keiintniss der 

 Fauna der Kreideformation von Hokkaido. P. 13 

 (159)— 18 (164). 

 This species is the most common form in our Cretaceous, 

 playing the rôle of the leading fossil of the upper Ammonite- 

 beds. It has long been known under the name of * Lytoceras 

 Sacga ' and the occurrence of the middle Cretaceous in Hokkaido 

 has been based by several authorities on this determination. 

 The writer took special care in studying this species, as it has 

 been often much confounded with allied forms. 

 Dimensions : — 



Diameter. 



Height of the 

 last wliorl. 



Breadth of the 

 hist whorl. 



AVidth of umbi- 

 licus. 



100. 

 34. 



38. 



42. 



1) The largest specimen ever found; from a cliff opposite the 

 mouth of the Panke-moyfibari, a branch of the Yûbarigawa. 



2) A specimen from Urakawa. 



3) A specimen from Urakawa (after Yokoyama). 



