CEPHALOPODA— AMMONOIDEA. 195 



side of the non-costate venter; costse remain single or bifurcate, 

 and in later stages cross the venter; the nodes may disappear in 

 old age, but in typical forms are retained ; median ventral furrow, 

 if present, is weak and interrupted by the costse; external saddle 

 large, stronger and longer than the first lateral ones; lateral lobes 

 pointed. Comanchic-Cretacic. 



340. D. spiniferum Whiteaves. (Figs. 1454, 1455.) Comanchic. 



Immature shells with sharp ribs bearing two or three rows of 



sharp nodes on either side of median ventral depression, and a 



Fig. 1454. Douvilleiceras spiniferutn^'wcvmoXnrQ \ndW\d\\di\. (After Whiteaves, Mes. 

 Foss., I.) 



similar number of nodes on lateral and umbilical portion, the two 

 sets being separated by broad depressions. Adult with spines 

 weaker or obsolete, the ribs increasing mainly by intercalations of 

 two shorter ones and becoming broader towards the venter. 



Queen Charlotte formation of Queen Charlotte Islands; also 

 Horsetown and Lower Chico of California; also (?) Eagle Ford 

 formation of Texas. 



This species has been regarded by some as identical with D. 

 mamillare Schloth of the European Gault. 

 341. D. stolitzkanum Gabb. (Fig. 1456.) Comanchic. 



Ribs alternating in size, covering the venter uninterruptedly; 

 tubercles not well defined, mainly shown on the coarser ribs ; they 

 occur in three rows on each side of the slightly depressed venter 

 and decrease towards the umbilicus, the larger ones are flattened 

 in the direction of the costae. 



Shasta of California. 



CLII. Metoicoceras Hyatt. 

 Involute shells, laterally compressed and strongly costate; costae 

 sometimes extending across the more or less depressed or grooved 



