102 



16 



[SENAtE 



GONIATITES ROTATORItrS. 



Fig. 16. Diagram showing form of septa produced in a plane. 

 Geological formation and locality. Same as the preceding. 



GONIATITES HYAS (n.s.). 

 Shell discoid : volutions fire, six or more, slender and flattened laterally, and 

 rounded upon the back; umbilicus very wide and shallow, showing two-thirds 

 or three-quarters of the width of each volution, a very small portion only being 

 embraced in each succeeding one. Siphuncle very small. Dorsal lobe narrow 

 and acute, reaching about as low as the first lateral lobe; dorsal saddle elon- 

 gate, broader than the dorso-lateral lobe or lateral saddle; dorso-lateral lobe 

 narrow, elongate, sublinguiform, and pointed below; lateral saddle of the form 

 of the dorsal saddle, but narrower, the apex midway between the dorsal and 

 ventral side of the volution ; ventro-lateral lobe of the form of the dorso-lateral 

 lobe, but a little shorter : ventral saddle broader and shorter than the dorsal 

 saddle. • 



This species is associated withthe two preceding ones, and is readily known by 

 the more slender volutions and broad umbilicus, as well as the abruptly undulated 

 septa. It bears some relation to G. chemungensis of Yanuxem (Report 3d Geol. 

 District N.York, p. 182, f. 1). 



17 



GONIATITES HYAS. 



Fia. 17. Form of the shell. Fia. 18. Diagram showing direction of septa. 



Geological formation and locality. In strata of the age of the Hamilton group 

 of N.York; at Rockford, Indiana. 



