JURASSIC AMMONITES FROM ECHIZEN 4 NAG A TO. 15 



by intervals of nearly n like breadth. The edge of the umbilicus 

 is nearly right-angled, and its wall perpendicular, so that if the 

 inner whorls were preserved in our specimen, they would appear 

 descending stair-like into their centre. 



The general form, the mode of eostation and the small 

 umbilicus with perpendicular walls make our species resemble 

 Harpoceras Lythense Young and Bird (Wright, Idas Ammonites, 

 p. 444, pi. LXIL, fi<js. 4-G) of the English Upper Lias; but 

 how far the resemblance extends, it is at present not possible to 

 make out from the imperfect state of preservation of our fossil. 



Locality : — Nishi-Nakayama. 



6. HARPOCERAS pp. 



PI. IV. Fig. 2. 



This is another flat, keeled, narrowly umbilicated shell, about 

 85 mm. in diameter, and with an umbilical width of 20 mm. 

 The ribs are sigmoidal as in the preceding species, but decidedly 

 denser and more numerous, the number reaching up to 70, and 

 near the mouth running out into many sigmoidal striations. The 

 umbilical wall is perpendicular. 



The form and outer sculpture show a great resemblance to 

 Harpoceras exaraium Wright (Idas Ammonites, p. 441, pi. LXIL, 

 jigs. 1-3) of the Upper Lias. 



Locality : — Nishi-Nakayama. 



7. CŒLOCERAS SUBFIBULATUM M. 



PL ITT. Figs. 3-6. 



There are several specimens of a Cœloeeras which may be 

 characterized as follows : 



