Mo. 1762. I W.'ir FOSSIL CROCODILE— GILmORE. 501 



In the matter of the splenial contributing to the symphysis, 

 Leidyosuchus may be considered ancestral to such Wasatch forms as 

 Crocodylus polyodon Cope and C. subulatus Cope. The relationship 

 of these forms is still further indicated by their reference by Professor 

 Cope to Diplocynodus a (Diplocynodon) on account of the presence in 

 the upper mandible of two adjacent enlarged teeth. Later'', how- 

 ever, both species were provisionally assigned to the genus Crocodylus 

 by the same authority. 



In Leidyosuchus and the gigantic Deinosuchus recently described* 

 by Dr. W. J. Holland, we have in the Judith River beds the first au- 

 thentic record of the appearance of procoelian crocodiles in the Cre- 

 taceous of the Rocky Mountain region. 



EXPLANATION OF PLATES. 



Plate 23. 



Skull of Leidyosuchus sternbergii. Cat. No. 6533, U.S.N.M. One-half natural size. 

 Seen from above 



e. mi., external narea; ex. occ, exoccipital; fr., frontal; i. /./., infratemporal fossa; 

 ju., jugal; /'/., lachrymal; mx., maxillary; n., nasal; o., orbit; occ, occipital con- 

 dyle; pa., parietal; p. /., postfrontal; p. fr., prefrontal; pmx., premaxillary; pt., 

 pterygoid; 7., quadrate; q.ju., quadrato-jugal; .s. /. /., supratemporal-fossa; sq., 

 squamosal. 



Plate 24. 



Skull of Leidyosuchus sternbergii. Cat. No. 6533, U.S.N.M. One-half natural size. 

 Seen from below. 



a. p. v., anterior palatine vacuity; b. occ, basioccipital; b. s., basisphenoid; m.e.c, 

 median eustachian canal ; m.r., maxillary; occ, occipital condyle; p.-, palatine; pmx., 

 premaxillary; />. im.. posterior nares; p. p. v., posterior palatine vacuity; pt., ptery- 

 goid; 7., quadrate; q.ju., quadrato-jugal; t. p.. transpalatine. 



Plate 25. 



Skull and jaws of Tjeidyosuchus sternbergii. ('at. No. 6533, U.S.N.M. One-half 

 na1 Ural size. Lateral view. 



ang., angular; '/., dentary; e. m. /., external mandibular foramen; ju., jugal; mx., 

 maxillary; pmx., premaxillary; 7., quadrate; 7. ju., quadrato-jugal; s. any., suran- 

 gular; sq., squamosal. 



Plate 26. 



Skull of Leidyosuchus sternbergii. Cat. No. 6533, CJ.S.N.M. Natural size. Posterior 

 view. 



h. ore., basioccipital; b. s., basisphenoid; c. a., foramen for carotic artery; ex. ore, 

 exoccipital;/. m., foramen magnum; m. e. C, median eustachian canal; oc c, occip- 

 ital condyle; j>i., pterygoid 7., quadrate; vn, x, xn, foramina for cranial nerves. 



" Sixth Ann. Kept. IT. S. Geol. Surv. Terr, for 1S72, L873, pp. 613-614. 

 '' Rept. ('. S. Geol. Surv. Terr., vol. :5, L884, p. 154, pi. 31, figs. L8-23. 

 c Annals of the Carnegie Museum, vol. ii, !!)()!», pp. 281-294. 



