Revieics — Prof. Co])e's Extinct Vertebrates of N. America. 471 



Extinct Dogs. — The Dogs are included by Prof. Cope in a single 

 family — the Canidce — which has been shown by other writers to pass 

 so impei'ceptibly by means of the genera Dinocyon and Hyanarctos 

 into the Ursidce, that it seems impossible to draw any distinction 

 between the two. Prof. Cope (p. 236) recognizes eight extinct ^ 

 American genera of the family, mainly distinguished by dental 

 characters of more or less importance. The Miocene European genus 

 Amphicyon is represented by several species ; and the same may be 

 said of the genus Cynodictis, which Prof. Cope identifies with Gale- 

 cynus, Owen ; the latter appearing to ourselves to be indistinguish- 

 able from Canis, and of later age than Cynodictis. The peculiar 

 American genus jElurodon appears to indicate a transition towards 

 the Hyeenoid Ictitherium ; and since Cynodictis comes extremely close 

 to some of the Viverridae, we learn how very intimate was the former 

 connexion between the now well-marked families of the Hyaenidae, 

 Viverridee, Canidae, and Ursidee. 



The Creodonta. — The serial position of the forms included in this 

 group have been already discussed in our preliminary remarks. 

 Prof. Cope includes in it the Mesonychidas (1), Hyaenodontidae (2), 

 Chrysochloridse (3), Centetidee (4), Leptictidee (5), Potaraogalidge 

 (Mythomyidae) (6), Talpidse (7), Oxy^nidte (8), and Miacidae (9). 

 Nos. 3, 4, 6, 7, are existing families of Insectivora, the remaining 

 five being extinct. The family Oxy^nid^e includes the genera 

 Pterodon and Oxycena; but the former appears so closely allied to 

 Hyeenodon that we are inclined to place all three in the same family. 

 Oxycena and Hycenodon occur in the Lower Tertiaries of Europe and 

 America, the latter being also represented in the higher Tertiaries of 

 India. The type genus of the first family is Mesonyx — evidently a 

 very generalized form, with the premolar and molar teeth but little 

 differentiated from one another. Space only admits of noticing a 

 few of the more interesting forms of the other families. The genus 

 Stypolophus, Cope, is included in the Leptictidae, and is identical 

 with the European Cynohycenodon, Filhol, which Prof. Gaudry iden- 

 tifies with Proviverra, Rutitneyer — the latter name having the priority 

 over both the others. Prof. Cope (p. 351) mentions a slight difference 

 in the form of the fourth upper premolar of the typical Proviverra, 

 but we are not inclined to regard this as of more than specific value. 

 The author regards the Leptictidge as the ancestral forms of the 

 modern Centetidae. The upper dentition of Stypolophus is very like 

 that of Pterodon, but the lower is quite distinct, and it is compared 

 by Dr. Filhol to that of the Opossums, while its brain is that of an 

 Insectivore. It is probable that we may follow Prof. Huxley^ in 

 regarding this genus as related both to the Hyasnodontidte and the 

 Centetidge. Another interesting genus included by Professor Cope 

 in the Leptictidae is that to which he applies the name Esthonyx, 

 but which has been shown in a late number of this Magazine 

 to be apparently identical with the European Eocene genus 



1 In Prof. Cope's table Cam's is erroneously included among the extinct genera. 



2 Proc. ZooL Sec. 1880, p. 284. 



