36 



AKT. 2. H. Y ABE : CRETACEOUS 



Dimensions : 



Diameter. 



Height of the last wliorl. 

 Breadth of tlie List wliorl. 

 AViclth of umbilicus. 



9^ 



The figured specimen from the Iknshumbets. 



Uesmoceras Dawsoni Whiïeaves from Cumshewa Inlet; 



measured from the figure on PI. XXVI. in Mes. Foss. 



vol. I., pt. 3. 

 3) Desmoceras Dawsoni Whiteaves from Cumshewa Inlet; 



measured from the figure on PL XXXVII. in Mes. 



Foss. vol., I., pt. 4. 

 Shell discoidal, compressed on the sides and rounded on the 

 ventral surface. Umbilicus narrow, with a steep wall and more 

 or less rectangular margin. Involution very deep, about | of eacli 

 volution being covered. Section of the whorl elliptical, higher 

 than broad. Surface with eight distant, very flexuous constrictions, 

 parallel to the lines of growth. Constrictions narrow, bordered 

 behind by an elevated rim which becomes more prominent and 

 bends strongly forward on the ventral surface. On aged speci- 

 mens, these constrictions become strongly sigmoidal as is shown 

 in the anterior portion of the figured example, and the lines 

 of growth, otherwise appearing as delicate striœ, also become 

 coarser. 



The suture line is only partly visible. The first lateral lobe 

 is about as long as the external lol)e and tripartite, but not so 

 deep and wide as in the case of Puzosia. The external saddle 

 as well as the two lateral ones are l)ipartite. 



The general outline, surface marking and suture line o^ the 

 Japanese species much resemble those of Desmoceras Dawsoni 



