102 PHRYNOSOMA DOUGLASSII. 



plates, and on the same plane, are four tubercles, slightly flattened and pointed, 

 the posterior largest. The inferior and external border of the lower jaw presents 

 a series of tubercles, those in front smaller and smooth, swelling only a little in 

 the centre, so as to give a festooned appearance; while those under the angle of 

 the mouth are larger, and slightly elevated into a pointed tubercle. Between this 

 series of tubercles and the labial plates, are interposed four or five rows of small 

 scales. The chin is covered with small, smooth, rhomboidal scales, of equal size. 



There are nine small tubercles, which surround the posterior and superior part 

 of the head, extending from the point of one meatus of the ear to the othei*. 

 These tubercles are disposed as in the Phrynosoma cornuta, yet are so slightly 

 developed as not to deserve the name of spines, for none of them exceed two lines 

 in length, and the central tubercle is so small as hardly to be distinguished; thus 

 the posterior part of the head loses that spiny appearance so remarkable in the 

 Phrynosoma cornuta and Phrynosoma coronata. The entrance to the external 

 meatus of the ear is sub- triangular, large above, smaller below. 



The neck is short, contracted at the back of the head, and covered above with 

 small scales, and small, slightly elevated pointed trihedral tubercles. The scales 

 of the throat are smooth and very small; the skin presents a transverse fold, 

 which tei'minates on the side of the neck, over a deep depression in front of the 

 anterior extremities, and here the margins of the fold are furnished with small 

 pointed spines. 



The body is short, flattened above, rounded or arched outwards at the flanks, 

 and is protected by small scales, interspersed with trihedral pointed tubercles, less 

 elevated than in the three other species, and arranged in four irregular rows on 

 each side of the vertebral line, and surrounded at their bases by smaller tubercles 

 of similar form. The vertebral line differs here also from the Phrynosoma 

 cornuta and Phrynosoma orbiculare in having several tubercles interposed in the 

 five or six rows of scales that cover it. The flanks are furnished with only a 



