CROCODILIANS, LIZARDS, AND SNAKES. 



679 



Fig. 139. 



Hemichirotes TRIDACTYLUS DUGfeS. 



X 2. 



From Dugfes. 



Bipes canaliculatiis Lacepede. Tail twice as long as head; preanal 

 scuta small, preceded by a transverse row of small scales, each of which 

 is perforated by a pore. Nasal plates well separated in front. Mexico. 



Hemichirotes tridactijlus Duges. Tail but little longer than head; 

 anus preceded by six plates of moderate size, and these by only two 

 pore-bearing scales on each side. Nasal plates widely separated by 

 contact of rostral and inter- 

 nasal. Guerrero, Mexico. A. [) Q. 

 Duges. Y/f^^^ ""^^"^ -~^^-<^ 2y 



EUCHIROTES Cope. ^' > ^^ _ ^ [ ) 



Euchirotes Cope, American 

 Naturalist, 1894, p. 436. 



Digits five, all clawed; nos- 

 tril in a single plate. Pre- 

 anal pores. Rostral plate 

 not prominent. Eye minute, 

 no eyelids. 



The characters of the scap- 

 ular and pelvic arches in this 

 genus are as follows: 



Scapular and pelvic arch present; fore limbs, but no hind limbs. 



Scapular arch. — For the first time in the history of scapular reduc- 

 tion we find the clavicle absent. No iuterclavicle nor precoracoid. 

 Supraclavicle osseous. Clavicle and coracoid osseous, coossified; no 

 coracoid cartilage. Sternum without costals, osseous, pentagonal, and 

 with a long xiphoid process. Ulna and radius well distinguished. 



Pelvic arch. — An elongate element on each side, directed downward 

 and a little forward, principally ilium, but with a short free distal 

 extremity, which represents one or both of the inferior elements. A 

 short curved cartilage represents the femur. The ilium is connected 

 by a cartilage with the extremity of a single diapophysis, and a short 

 free segment corresponding to this cartilage articulates with the ver- 

 tebra whi(!h follows. 



The scapular arch of Bipes canaliculatus Lac.«^pMe has been described 

 and figured byMiiller,' andbyDumeril and Bibron,^ both with omission 

 of pelvic arch. The description and figure which I gave^ as referring 

 to that species, was really taken from the Euchirotes bijmrus^ of the 

 distinctness of which I was not at that time aware. Miiller says of 

 tlie former species "that the clavicle and scapula are fused into a 

 single piece." This is probably an error, as there is apparently no 

 clavicle, as may be seen by comparing the figures given in the present 

 paper. Neither Miiller nor Dumeril and Bibron detected the rudi- 

 mental pelvic arch. Before I was aware of the difference between 



' Zeischr. f. Physiol., IV, 1831, pi. xxi, tigs. 11, 12. 

 2Erpt<tologie Go'uerale, Atla», pi. VII, figs. 1, 2. 

 3 Journal of Morphology, 1892, p. 240. 



