492 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



vol. 38. 



mosl robust tooth of the upper dental scries. The sixth, seventh, 

 eighth, and ninth are much reduced in size, but the tenth and eleventh 

 alveoli appear to have carried larger teeth. From this point, however, 

 to the end of the series, the teeth gradually diminish in size toward 

 the back. In the lower mandibular series all of the alveoli and three 

 of the teeth are preserved. The front teeth of the symphysial region, 

 that is, the first to the fourth, were directed obliquely outward. This 

 peculiarity is somewhat manifest as far back as the eleventh of the 

 series, back of which an upright position is maintained. The dental 

 series of the anterior half passes in a curve from the outer to the inner 

 side of the dentary. The fourth tooth was probably the largest of 

 the lower series, although, judging from the alveoli, the third must 

 have been approximately the same size. The fifth to the tenth were 

 small. The eleventh, twelfth, and thirteenth were slightly and about 

 equally enlarged, and those posterior to the thirteenth gradually 

 decrease in size. 



( 'omparative measun merits of skulls. 



Width between outer edges of quadrates, posteriorly 



Height of occiput. In median line, from upper surface of parietal to anterior edge 



of opening of median eustachian canal 



Height of foramen magnum 



\\ lath of foramen magnum 



Height of basioccipital, in median line 



Breadth of basioccipital al midheight 



Breadth of condyle of quadrate 



Height of condyle of quadrate at center 



Breadth Of t hfe upper surface of parietal, posteriorly 



Length of upper surface of parietal, In median line 



Distance of posterior end of preserved surface of narial passage to anterior edge of 



opening of median eustachian canal 



•i Est Imated. 



Mandible. The parts preserved of the lower jaw consist of the left 

 ramus almost entire, lacking only the coronoid and portions of the 

 articular, and the anterior portion of the righl ramus as far hack as 

 the alveolus for the eleventh tooth. 



The mandibular symphysis is short and composed of the spleniaJ 

 and dentary. In Leidyosuchus canadensis the splenial participation 

 in the symphysis is about one-fifth of its total length, while in L. 

 sterribergii it is somewhal less. In this particular, among American 

 brevirostrate crocodiles, Lndyosuchus is approached by GrocodUus 

 polyodon of the Wasatch and Bottosaurus from the Cretaceous of New 

 Jersey, in the hitter the splenial reaches the symphysis without con- 

 tributing to it . 



On the dorsal border of the left ramus, alveoli for twenty-one teeth 

 can be clearly disl inguished. 



