LIFK 



481 



Retreatal tracts of marine life. As in previous transition 

 epochs when epicontinental waters were largely withdrawn, the 

 marine faunas found special refuge in certain embayments or border 

 tracts which, in connection with the coastal belts, permitted them 



411. MARINE PERMIAN FOSSILS, a-f, Cephalopods: a, Mcdlicollia 

 i White; b and c, Waagenoccras cumminsi White; d and e, Popanoccras icalfottl 

 White, tlirec forms of ammonoids with sutures more complicated than in earlier 

 forms; /, Orlhoceras rushcusis McCh., one of the last of the orthoceratites. g-j, 

 Pelecypods: g, Pseudomonotix hawni (M. and W.); /', ^f \\ilhui p<rniian<i (Swall.); 

 nlapccten occidcnliilis (Shum.);j, Sedgwickia tvpckaeiisis (Shum.). k, Mur- 

 chisonia sp., a gastropod. 



