654 



GEOLOGY. 



complexly lobed. A transition from the simply lobed goniatites to 

 forms with more complicated sutures had taken place as far back as 

 the Kinderhook epoch (see Fig. 235, j). In the latter part of the 



Fig. 306. — The Marine Permian Fauna: Cephalopoda: a, Medlicottia copei White; 

 b and c, Waagenoceras cumminsi White; d and e, Popanoceras walcotti White; 

 three forms of ammonoids with more complicated sutures than were present in 

 earlier forms; /, Orthoceras rushensis McCh., one of the last of the orthoceratites. 

 Pelecypoda: g, Pseudomonotis hawni (M. & W.); h, Myalina permiana (Swall.); i, 

 Aviculopeden occidentalis (Shum.); /, Sedgwickia topekaensis (Shum.). Gastropoda: 

 Murchisonia sp 



Permian period, forms with still more intricate sutures (Fig, 306, c and 

 e) ) approaching those of the characteristic ammonites of the Mesozoic, 

 became conspicuous. The genera Medlicottia (Fig. 306, a), Waageno- 



