8 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



A front foot, previously described as Icthycanthus platypus (Proc. Am. 

 Phil. Soc, 1877, p. 54), was in this paper referred to the genus Eryops. This 

 reference is exceedingly doubtful. 



In 1887 appeared that portion of Zittel's Handbuch d. Paleontologie, 

 dealing with the more primitive fishes. The following disposition is made 

 for the Permian fish : 



Subclass Selachii. 



Suborder Plagiostomi. 

 Family Xenacanthides. 

 Genus Didymodus. 

 Orthacanthus. 

 Suborder Batoidei. 

 Family Petal odontida. 

 Genus Janassa. 



Thoracodus. 



Subclass Dipnoi. 

 Order Ctenodipterini. 

 Genus Ctenodus. 

 Ptyanodus. 

 Gnathorihiza. 

 Strigilina. 

 Order Sirenoidea. 



Genus Ceratodus. 



Subclass Ganoidei. 

 Order Crossopterygides. 

 Family Rhombodipterini. 

 Genus Ectosteorhachis. 



In 1888 appeared the portion dealing with the Amphibia. 

 Diplocaulus is placed as uncertain, in the family Microsauria of the sub- 

 order Lepospondyli. The others are arranged as follows: 



Suborder Temnospondyli. 



Division A. Rhachitomus vertebrae. 

 Genus Trimerorhachis. 



Eryops {Rhachitomus). 

 Epicordylus (Parioxys). 

 Zatrachys. 

 Acheloma. 

 Anisodexis. 

 Division B. Embolomerous vertebrae. 

 Genus Cricotus. 



In 1889 Cope published a synopsis of the families of the vertebrates (42). 

 In this he divides the Elasmobranchii into two orders, which he defines as 

 follows : 



"A basioccipital and exoccipital dements; actinotrichia; baseosts and 

 axonosts continuous with neural spines; paired fins with a single basal 



axonost, and numerous others in line with it; claspers simple Icthyoiomi 



No basi- or exoccipital; median baseosts and axonosts continuous with 

 vertebral spines; several axonosts to paired fins, and numerous base- 

 osts; claspers complex; actinotrxhia Selachii" 



