OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 411 



from the position of the splenial in other reptiles. Baur,^ in 1895, 

 discovered in the extinct Toxochelys a bone that corresponds to the 

 true splenial of other reptiles, and recognized for the first time that 

 the so-called splenial of other turtles really is homologous with a 

 dermal element which is either wholly wanting or is indistinguish- 

 ably fused with the articular in all other reptiles then known. 

 Unfortunately, assuming that the bone so called in the Chelonia was 

 the true splenial, he changed the names of the elements in other 

 reptiles to correspond, naming that originally called the splenial by 

 Owen the presplenial, causing thereby much confusion in nomen- 

 clature. In 1 903 I recognized^ for the first time in an another 

 reptile this dermogenous element, in the plesiosaurs, and corrected 

 Baur's error by naming it the prearticular, retaining the names of 

 all the other elements as originally applied by Cuvier and Owen. 

 Soon afterward Case recognized the prearticular in the Pely- 

 cosauria, and Branson in the Stegocephalia. Since then the name 

 has come into general use, though other names were later pro- 

 posed for the same bone (dermarticular Kingsley, goniale Gaupp). 

 Five years ago I expressed the conviction that a separate pre- 

 articular would be found characteristic of all early reptiles; we 

 now know that to be the fact. Typically the bone overlies the 

 inner side of the articular, forming the inner margin of the supra- 

 meckelian orifice, and the posterior and superior margin of the 

 posterior inframeckelian foramen, when it is present, its anterior 

 end intercalated between the splenial and the coronoid. In other 

 words, it has precisely the same relations as has the anterior inner 

 part of the angular in the crocodiles (Fig. 12), in which no evidence 

 has so far been adduced of a prearticular ossification. One wonders 

 whether embryological investigation may not show a fused condi- 

 tion of prearticular and angular in these reptiles; in which case 

 the so-called angular would properly be called the angular- 

 prearticular, just as the so-called articular of lizards is really the 

 articular-prearticular . 



In all later reptiles the coronoid is a small element occupying 

 the eminence of the mandible back of the teeth, articulating with 



' Baur, Anat. Anzeiger (1895), p. 412. 



^Williston, Field Columh. Miis. Publ., No. 73, p. 30. 



