492 REPORT OF NATIONAL MUSEUM, 1898. 



Scapular arch. — luterclavicle wanting; clavicles present, osseous, 

 meeting medially. Scapula cartilaginous; coracoid osseous. A large 

 coracoid cartilage, which is continued proximally into the short and 

 narrow precoracoid cartilage. Sternum without rib connections, of a 

 transversely crescentic form, the convexity anterior, with some ossific 

 deposit at the middle, on each side of the median line. 



Pelvic arch. — The three elements fused into a single piece, of which 

 the ilium forms a slender proximal part and the distal elements an 

 oval plate, concave anteriorly and convex posteriorly; the whole 

 entirely lateral in position, and having a general resemblance to the 

 corresponding parts of Ophisaiirus. Ilium short, its proximal extremity 

 in contact with a very robust diapoi)hysis of a single vertebra. 



Observations. — The absence of the interclavicle Justifies the retention 

 of the genus Dopasia Gray as distinct from Ophisaurus. I have 

 examined two skeletons of the T). f/racilis and a half dozen of those 

 of 0. ventralis. 



The characters of Ophisaurus are pointed out under that genus. 



The viscera do not display any exceptional features, except as to the 

 serpentiform genera referred to under tlie head of Diploglossa. The 

 mesenteries are of the typical character, modified in Ophisaurus by 

 the reduction of the left lung. The hepato ventral sheet is very near 

 the left margin of the liver in Pseudopus apus, and the gastrohepatic 

 and right hepatic are near together when slack. 



OPHISAURUS Daudin. 



Opliisaurua Daudin, Hist. Rept., VII, p. 346. — Fitzinger, N. Classif. Rept., 1826, 

 p. 20. — Wagler, Syst. Amph., 1830, p. 159. — Wiegmann, Herp. Mex., 1834, p. 

 11.— DuM^RiL and Bibron, V, 1839, p. 421.— Gray, Cat. Liz., 1845, p. 55.— 

 Boulknger, part. Cat. Liz. Brit. Mus., 1885, II, p. 279. 



Hyalinus Merrem, Tent. Amphib., 1820, j). 79. 



Body serpentiform, without external trace of limbs. A deep lateral 

 groove from near head to anus. Scales hard, bony, in transverse 

 series. An external ear, and scaly eyelids. Nostrils lateral, in a single 

 plate. Tongue arrow-shaped, notched, and flat anteriorly, where it is free 

 for about half its length. Palatine teeth. Tail much longer than body. 



The genus Ophisaurus is similar to the Gerrhonoti in essential charac- 

 ters, but differs in the absence of limbs. The fold on each side is 

 occupied by a soft skin which connects the dorsal and the ventral sheets 

 of plates, the latter folding or lapping over the upper and concealing 

 its lower edge. The plates on the body are quadrate and arranged in 

 transverse series, the dorsal and ventral not corresponding in size and 

 separated, as stated. On the tail the scales are in whorls, or bony rings, 

 between which fractures occur very readily. 



In this genus the skeleton resembles in many respects GerrhonoUis, 

 while presenting some important differences, which will be indicated 

 below. Premaxillary with elongate spine above, and concave palatal 

 margin interrupted by a short posteriorly produced angle on the middle 



