470 Reriews — Prof. Cope's Extinct Vertebrates of N. America. 



depend to a great extent on the mode of thouglit of each individual 

 writer — a more complex system appearing to one mind to convey 

 best the idea of mutual affinities, which would be equally well 

 conveyed to another by a simpler arrangement. 



With these preliminary remarks we may proceed to a short notice 

 of the various memoirs quoted above. 



Bhinoceroses and their Allies. — The Ehinoceroses are divided into 

 the two families Hyracodontidee and Ehinocerotidae (Khinoceridse) ; 

 the latter being split up into the genera Aceratherium (1), Dicer a- 

 therium (2), Aphelops (3), Geratorhinns (4), Zalabis (5), Bhinoceros 

 (6), Atelodus (7), and Ccelodonta (8). Zalabis was made for the 

 reception of the Sivvalik Bhinoceros sivalensis, but the characters on 

 which it was founded have been shown in the publications of the 

 Geological Survey of India to have originated in a mistake. We 

 are inclined to follow the view of Prof. Flower in including Nos. 4, 

 7, 8, and perhaps 2, in Bhinoceros. The European species of Acera- 

 therium have no nasal horn, but are furnished with four anterior 

 digits ; while the American hornless forms grouped under Aphelops are 

 distinguished by having only three anterior digits, and thereby agree 

 with the existing species of Bhinoceros. Using Rhinoceros in the 

 wider sense indicated above, we are inclined to include Aphelops in 

 Aceratherium ; and we must then acknowledge that there is scarcely 

 more than an arbitrary distinction between the latter and Bhinoceros, 

 although its retention as a genus may be advisable. The logical 

 sequence of cutting down the genera of Prof. Cope's Ehinocerotid^ 

 from eight to two, and the consequent relegation of his generic 

 characters to a minor value, will be the inclusion of his Hyracodon- 

 tidse in the same family. 



Extinct Gats. — The cat-like animals Prof. Cope divides into the 

 NiraravidjB and Felid^ ; the former comprising primitive generalized 

 forms now entirely extinct, and the latter both the extinct sabre- 

 toothed Tigers and all existing Cats. Hei'e, again, we are afraid we 

 must differ from the author as regards his separation of these two 

 families, and his retention of Dr. Gray's division of the existing Cats 

 (excluding Cyncelurus) into several genera. The most generalized 

 animal which can be called a " Cat " in the widest sense of the word 

 seems to be the Procelurus of the French Phosphorites, which pre- 

 sents many musteline affinities, and indicates how difficult it is to 

 form any accurate family divisions in the older mammals. From 

 this form there is a gradual advance through the genera Pseudcelurus, 

 Archcelurus, JEliirogale, Pogonodon, etc. (most of which have more 

 teeth than existing Cats), to the sabre-toothed Tigers and their modern 

 allies. The sabre-toothed Tigers (which Prof. Cope divides into Drepa- 

 nodon and Smilodon, but which we prefer to group together under 

 the older name Machcerodus) are well represented in America ; and 

 all European museums must envy the magnificent skeleton of 

 Machcerodus [Smilodon) necator figured in the frontispiece to this 

 memoir. The phylogeny of the Cats, as worked out by Professor 

 Cope and Dr. Filhol, indicates very fully the former history of the 

 group. 



