OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 415 



Fig. 15; and Captorhinus, Fig. 16). Photographic copies of the 

 mandible of Dimetrodon, precisely as here figured (Fig. 13), were 

 distributed to some of my correspondents in August of 1913. I 

 was not then confident of the continuity of the coronoid bone 

 throughout, and so briefly described it in Science of October 10, 

 19 13, as possibly, though not probably, composed of two bones, 

 the anterior one of which I called the alveolar. Later material 

 satisfied me that there is but a single bone. Dr. Broom^ refers to 

 this description as of a distinct alveolar bone; doubtless it was an 

 oversight, since he re- 

 ceived a copy of Fig. 

 13 in August, as also 

 my figures of the 

 mandibles of Trime- 

 rorhachis and Lahid- 

 osaurus, before he 

 wrote his paper. 



Since the foregoing 

 went to the printer I 

 have received from 

 Dr. Broom another 

 paper, published Feb- 

 ruary 24, 1914, con- 

 taining a description 

 and figure of a man- 

 dible of a pelycosaur 



preserved in the National Museum, which he doubtfully referred to 

 either Dimetrodon or " Naosaurus" {Edaphosaurus) ! The only addi- 

 tion this paper makes to our knowledge is the precise connection 

 between the coronoid and prearticular. He determines, however, 

 without hesitation or doubt a suture separating the coronoid into 

 two bones, the anterior of which he calls the precoronoid. At 

 my request, Mr. Gilmore kindly sent me the specimen upon which 

 Broom's studies were based. It is very clearly a species of Dime- 

 trodon. I give herewith a more accurate figure of the specimen 

 (Fig. 14). All the sutures, aside from the one in question, are 



I Broom, Bull. Amcr. Mas. Nat. Hist. (November, 1913). 



Fig. 16. — Trinacromermn oshorni Williston: Left 

 mandible to sjonphysis, inner side, after WUliston, 

 1903; B, Captorhinus aguti Cope, left mandible, from 

 within; C, the same, outer side. Explanations as in 

 Fig. 13- 



