NATURAL SCIENCES OF PHILADELPHIA. *?! 



M 



Length of head and body 064 



" of head ' . . .006 



Width of head ' . . .004 



Length of tail (extremity lost) OHS 



" of fore limb . 0027 



Color, a dark reddish-brown; a dorsolateral series of pale spots 

 one each side, separated by an average width of eiglic scales. 



From Xauta on the Peruvian Amazon ; obtained by Professor 

 Orton. Various peculiarities distinguish this little saurian from 

 the Opliiognomon Irisanale, among which are the more numerous 

 scales, and mutual contact of the second pair of infralabials. 



Gerrhosteus prosopis, gen. et sp. nov. 



Dentition opisthoglyph ; cranial scuta normal except that the 

 prefrontals are united into a continuous shield. A loreal and a 

 preocular ; pupil vertical. Anal scutum undivided;- subcaudals 

 two ro'wed. Scales poreless, smooth, subequal. The neural 

 spines of the vertebrae each supporting a shield-like expansion, 

 giving a T-shaped cross section, which is divided by a median 

 groove. 



This genus is the first of the Ophidia known to possess the 

 osseous expansions common to some genera of Batrachia, etc., of 

 the western tropical part of the Neotropical region, and the mio- 

 cene salamanders of the genus Chelotriton^ Pom. The great de- 

 velopment of the neural spine is not nnlike that seen in frogs of 

 the genus Dendrohaten^ which are characteristic of this region. 

 The series of closel}^ consecutive bony parallelograms, forms an 

 elevated rib throughout the length of the animal, which is clearly 

 visible through the skin, which is not involved in it, though thiu 

 and closely adherent. Tlie structure would appear to be an addi- 

 tional protection to the spinal cord from blows or falling objects. 



Char. Specif. General appearance that of a L3'codont, while 

 the dental and scutal characters ally it most to Oyrrhopus. 

 Head an elongate oval, very distinct from the narrow neck ; body 

 fnoderatel}' stout ; tail short, terminating in a corneous spine. 

 Rostal plate small, not prominent, intern asals small. Frontal 

 broad as long, straight in front with two subequal lateral facets 

 for the preocular and the short superciliary. Parietals elongate. 

 Nasal apparently single, large, descending nearly to the edge of 

 the lips. Dorsal small, not longer than high. Preocular large, 



