124: SYNOPSES AND DESCRIPTIONS. 



Subcaudals bifid; 



scales in 27 — 29 rows asper. 



scales in 23 — 25 rows atrox. 



subcaudals entire; 



scales in 27 rows affinis. 



Trigonocephalus asper. 



var. n. C. LANCEOLATI. 



Body long, tapering to head and tail ; head large, broad behind, pointed 

 and angular in front; crown flat, covered with small keeled scales. A pair 

 of internasals, in contact behind the rostral; behind these on each side a 

 larger plate rests against nasal, loreal and anteocular, but is separated 

 from the large supraciliary by a small scale. Rostral subquadrangular. 

 Nasal in two parts, anterior larger. Loreal quadrilateral. Anteoculars 

 two; upper much larger, sometimes divided; lower half as long, narrow. 

 Suboculars narrow, fused, separated from the labials by a scale. Postocu- 

 lars 2 — 3. Labials seven, posterior four large. Infralabials 10 — 11. Sub- 

 mentals one pair, not in contact with the mental. Scales keeled, in 27 

 (27 — 29) rows. In large specimens the keel of the median rows is swollen, 

 and does not reach the end of the scale. 



Reddish-brown, with Y-shaped marks of light color on the flanks, which, 

 Avhen opposed, inclose rhombs of the ground color or lighter. When reg- 

 ularly opposed the pattern resembles that of Crotalus horridus or Lachesis 

 mutus. Flanks lighter with one or more series of spots near the abdomen 

 and upon its edge. Belly and sides of head yellowish, the former mot- 

 tled posteriorly, the latter with a brown line from the eye to a point near 

 the angle of the mouth. The specimens described were taken at Obisjio, 

 on the Isthmus of Darien, by Dr. Maack. Compared with specimens from 

 Martinique and St. Lucia, they are distinguished by brighter colors and 

 swollen keels. The pattern of markings is similar. The numbers and 

 shapes of labials and other head-plates are the same. «. 



Trigonocephalus atrox. 



Colttber atrox Linne", 1754, Mm. Ad. Fridr., Tab. 22, fig. 2, and Gmelin, 1788, Syst. Nat., 1107. 

 Cophias atrox Merrem, 1820, Tent. Syst., 154. 



Body long, moderately slender, tapering to head and tip of tail; head 

 broad behind, pointed in front, crown flat, covered with small keeled scales ; 



