++. TRIMORPHODON 



Brown, Proc. Acad. Nat. Sci. Phila., 1901, p. 91; Stejneger, 

 Proc. U. S. Nat. Mus., Vol. XXV, 1902, p. 157; Mocquard, Miss. 

 Sci. au Mexique, Pt. Ill, Kept., 1908, p. 909, pi. 74, fig. I, la-b; 

 DiTMARS, Reptile Book, 1907, p. 389; Van Denburgh & Slevin, 

 Proc. Cal. Acad. Sci., Ser. 4, Vol. 3, 1913, p. 423; Stejneger & 

 Barbour, Check List N. Amer. Amph. Rept., 1917, p. 104; Van 

 Denburgh & Slevin, Proc. Cal. Acad. Sci., Ser. 4, Vol. XI, 1921, 

 pp. 52, 70; Nelson, Mem. Nat. Acad. Sci., Vol. XVI, 1921, pp. 114, 

 115. 



Description. — Head very distinct from neck, the tem- 

 poral regions being swollen. Snout rather short, rounded, 

 somewhat projecting. Rostral plate large, broader than 

 high, bounded behind by internasal, anterior nasal and first 

 labial plates. Plates on top of head are a pair of internasals, 

 a pair of prefrontals, a frontal, supraocular of each side, and 

 a pair of rather short parictals. Two loreals placed one in 

 front of the other. Often a small subloreal in the notch 

 between the second and third supralabials, below the poster- 

 ior loreal, and in front of the inferior preoculars. Preocu- 

 lars three or two. Postoculars three. Temporals normally 

 three followed by four, sometimes 2+3. Usually nine 

 (rarely seven) superior labials, the sixth or seventh largest, 

 the fourth and fifth reaching eye. About 12 (sometimes 10 

 or 1 1 ) inferior labials, the first pair meeting on the median 

 line. Genials in two pairs, the anterior much larger. Scales 

 on body smooth, in 20, 21, 22, or 23 rows. Anal plate 

 divided. Gastrosteges varying in number at least from 231 

 to 236. Urosteges in two series of about 70 to 74. 



The ground color above is gray. The head is crossed 

 by a more or less indistinct grayish band which involves the 

 anterior part of the prefrontals. The posterior half of these 

 plates and the anterior portion of the supraoculars are crossed 

 by a brown band with very concave posterior border. This 

 band is continued upon the inferior postocular and the sixth 

 supralabial. A broad band begins on each side of the center 



