CEPHALOPODA— AMMONOIDEA. 



139 



206. A. rotatorius deKoninck. (Fig. 1392, j-^.) Mississippic. 



Sides sloping gently to rounded venter ; umbilicus almost closed, 

 not showing inner whorls ; ventral lobe tongue-shaped, lateral lobes 

 narrow and pointed. 



Kinderhook of Indiana (Rockford Goniatite bed) ; Waverly of 

 Ohio; also in Europe in same horizon. 



LXXXL MuENSTEROCERAS Hyatt. 

 Evolute, compressed or discoidal goniatites, with highly arched 

 whorls and moderately wide umbilicus. Sutures with angular, 

 superior, lateral lobe, and acute second lateral lobe outside of 



Fig. 1392. a-c, Gonioloboceras welleri^ shell ^, and suture enlarged ; d^ e, Muen- 

 steroceras oweni, shell X % \ f-^^ ^' pc-rallelum^ shell X /^> and suture enlarged ; 

 i-k, Aganides rotatorius^ shell X K> ^"^ suture enlarged. (All after J. P. Smith.) 



umbiHcus; ventral lobe narrow, with small, notched saddle; sur- 

 face smooth. Mississippic. 



207. M. oweni (Hall). (Fig. 1392, i/,^.) Mississippic. 



Laterally flattened ; height and width of whorl about same ; 



embracing to one half the depth of whorl; umbilicus rather large, 



