PLATE IV. 



PAGE. 



Fig. 1. Gomphoceras? Hyatti Whitf. (See also Plate V) 427 



1 Side view ol an imp rfect specimen showing the rapid contra :tion of the dorsal 

 side toward the aperture. 



Figs. 2-3. CyrToceras cretacetjm Whitf. 430 



2. Dorsal view of an imperfect specimen, slightly restored in the outer chamber, 



showing the siphuncle in the lower part. The lirations in the lower part are 

 produced by the advancing scars of muscular impressions. 



3. Side view of another individual, a part of the separate portion removed to show 



the siphuncle. 



Fig. 4. Gomphoceras Sciotense Whitf. 428 



4. Side view of the outer chamber of the specimens Figs. 13 and 14, on Plate II, 



showing the depth of the septum. 



Fig. 5. Gyroceras seminodosum Whitf 431 



5. Side view of the specimen describe:!, showing the absence of nodes on the inner 



whorls. On the dorsum of the outer volution a fragment of the shell re- 

 mains indicating its thickness. 



