SYNOrSES AND DESCRIPTIONS. 115 



nasals large, narrowing toward the rostral; postericn- higher and shorter. 

 Loreals two, or upper fused with prefrontal. Anteorbitals two, upper large, 

 lower elongate, narrow. Three plates surround the pit, in fi'cjnt of which 

 is a group of smaller scales (7—11). Sub and postorbitals 6 — 7. Ante- 

 rior orbital separated from the sixth labial by two scales. Cheek scales 

 larger than labials, smooth. Labials 16 — 17, sixth largest. Anterior pair 

 of infralabials small, not in contact. A pair of moderately large and broad 

 submentals, separated in the anterior half of their length by a pair of wedge- 

 shaped plates. The mental is separated from the submentals, and the 

 anterior infralabials from each other by a pair of polygonal plates somewhat 

 larger than the labials. Scales in 27 rows, striate and keeled, except the 

 outer two. Ventrals 1884-24. Rattle resembling that of adamanteus. In 

 the specimen described, which is quite small, fi'om the hindmost ring of the 

 rattle to the fifth there are eight which show a very slight increase in size ; 

 in front of these the next has suddenly enlarged, and fi'om this to the twelfth 

 and most recent the size remains the same. 



Light gi'eyish-brown. Shapes of markings similar to those of C. lucifer. 

 About thirty-three rounded, dark-edged spots on the back, separated by 

 whitish spaces of a scale in wddth, and twice as many small spots on the 

 lower edge of the flank, which also bears faint indications of a series alter- 

 nating with the dorsal. Tail, with a dorsal series of black spots opposed to 

 others on each side, with which they are more or less confluent. Belly uni- 

 form white or clouded lightly with olive near the flanks. Head nearly 

 uniform brownish -grey, with faint indications of a light band from the 

 frontal region to the central and hinder labials. A very faint band of light 

 behind the eye toward the angle of the mouth. Total length 20 inches; 

 tail 1| inches. Hab. Cedros Island, Lower California. Prof. Alex. Agassiz, 

 two specimens, 



Ceotalus horridus, pi. IX, Jig. 1. 



Linne, 1758, Systema Nat, ed. X, I, 214. 



Stout, elongate fusiform; head distinct, triangular, very broad behind; 

 neck small; tail short, thick, slightly compressed, outlines of the rattle 

 approaching the parallelogramic. Head with one or more pairs of rugose 

 plates in front. A pair of internasals, generally present, separated fi-om 

 the large elongate supraciliary by a single plate. With or without a pair 

 or more of small frontals. Rostral higher than broad. Nasal in two por- 



