4i6 



5. W. WILLISTON 



clearly shown, especially in connection with my previous figure 

 which Dr. Broom had at the time of his studies. That there is a 

 real suture dividing the coronoid is not impossible, but there is 

 nothing in the specimen to prove that it is not a crack, and not 

 until it is corroborated by additional material should his figure 

 be accepted as certain. Dr. Broom has made mistakes before in 

 his hasty identification of cracks as sutures, and this may be 

 another one. Dr. Broom states that he has "recently" seen a 

 copy of my figure of the Dimetrodon jaw as here given (Fig. 13). 

 *' Recently" is evidently here used in a relative sense, since he 



Fig. 17. — T rimer or hachis alleni Case: A, right mandible, inner side; B, the 

 same, outer side; C, D, E, sections of mandible as designated; psp, postsplenial; 

 cor, coronoid; icor, intercoronoid; poor, precoronoid. Other explanations as in Fig. 13. 



first saw the figure before he began his study of the American 

 mandibles, in August, more than three months before he studied 

 the specimen in the National Museum. 



AMPHIBIANS 



In the structure of the mandible the amphibians are remarkably 

 intermediate between the early reptiles and the contemporary 

 crossopterygian fishes, differing from the latter chiefly in the 

 reduced number of coronoids, and from the former chiefly in the 

 possession of two additional coronoids and a splenial. 



