236 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



EXPLANATION OF PLATE XXVL 



(From a photograph by Franklin, Palo Alto, California.) 

 Placenticeras pacificum, sp. nov. 



Adult shell, diameter 172 mm., six and a sixth coils, natural size. 

 Henley, California. Type specimen, property of Frank M.Ander- 

 son, Yreka, California. 



