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THE AMERICAN NATURALIST [Vol. XLII 



Stiitze fiir eine solche Annahme, dass ein pigmentoser Degenera- 

 tion anheimgefallenes Organ einer Yerjiingung (lurch Erwerb- 

 nng einer neuen Punktion fahig ware . . . ???-— und dann 

 Bchliesst gar der Satz, the agens of rejuvenescence being some 

 form of natural selection ! . . . heisst das etwa nicht, den Spot- 

 tern iiber die Nolektionstheorie Wasscr auf die Miihle tragen?! 

 Es wird Einem ja sehwindlig. wenn man an diesen babylonischrii 

 Turnbau nur denkt ! " AT. E. Rittee. 



VERTEBRATE PALEONTOLOGY 

 Pelycosauria of North America. 1 — There are few groups of 

 animals at the present day of greater interest to the paleon- 

 tologist and evolutionist than the extinct air-breathers of the 

 Permian ; and, of the Permian vertebrates, those of America, in 

 their abundance, variety and excellence of preservation are easily 

 the chief. As is well known, Professor Case has, for the past 

 ten years or more, given much intelligent attention to the Per- 

 mian reptiles of America, and especially to the group which he 

 has described in the present handsome memoir as the "suborder" 

 Pelycosauria. And the writer is inclined to think that he is a 

 little too conservative here, for he believes that the structural 

 characters are so diverse, so widely divergent from those of the 

 modern Sphenodon. that to include them both in one and the 

 same order is to hinder rather than advance an intelligent 

 taxonomy of the reptiles. Mr. Case has given in the volume a 

 complete history of the literature of the group, a taxonomic 

 revision, a thorough discussion of the structural characters of 

 the pelycosaurs, and the facts of their range and distribution. 

 He has not, rather wisely, entered very fully into the many 

 philosophical matters that the animals suggest. He expresses 

 the opinion, however, that the pelycosaurs represent a highly 

 specialized and short-lived branch of the rhynchocephalian stem, 

 and in that he will probably have the concurrence of most 

 paleontologists. But, to the writer, this does not seem altogether 

 certain. The group has an abundance of generalized char- 

 acters in the vertebra, pectoral and pelvic girdles, eleithra, etc., 

 the specialization consisting, for the most part, in the extra- 

 ordinary and most bizarre elongation of the vertebral spines, the 

 teeth, etc. His reasons for the grouping he makes are chiefly to 

 be found in the temporal region of the skull; and the writer 

 1 Case, E. C. Kevision of the Pelycosauria of North America. Memoir 

 of the Carnegie Institution of Washington, pp. 1-176, pis. I-XXXV, 1907. 



