140 CALIFORNIA ACADEMY OF SCIENCES. [Proc. ',d Sek. 



EXPLANATION OF PLATE V. 



Page. 

 Desmoceras hoffmanni Gabb, 97 



Figs. 120-121. Young adult shells. 



Figs. 122-123. Younger shells. 

 Lytoceras ( Tctraffonites) jacksoncnse, sp. nov 82 



Figs. 124-125. Adult shells, without body-chamber. 

 Holcodiscus, cf. H. theobaldiatitis Stol. ioi 



Figs. 126-127. Young adult shells; natural size. 

 Desmoceras colusaense, sp. nov. 96 



Figs. 12S-129. Adult shell; one-half natural size. 

 Hamites arinalmn, sp. nov. 89 



Fig. 130. Side view, body-whorl . 



Fig. 131. Ventral surface, showing spines. 



Fig. 132. Cross-section of same. 



