112. ATKACTUS. 305 



one postocular (exceptionally two); temporals 1+2; six upper 

 labials, third and fourth entering the eye ; two pairs of chin-shields, 

 posterior half as long as anterior. Scales in 17 rows. Ventrals 

 172-179 ; anal entire ; subcaudals 24-32. Uniform dark plumbeous 

 above, margitis of scales lighter ; a yellow occipital bar may be 

 present, crossing the parietal shields ; ventrals white, mottled with 

 leaden, or tiniform leaden. 



Total length 455 millim. ; tail 45. 



Mexico (San Luis Potosi and Hidalgo). 



6. Atractus longiceps. 



Rhabdosoma longiceps, CoiJe, Proc. U.S. Nat. Mus. ix. 1886, p. 189. 



Agrees in most respects with A. latifrontalis, but snout more 

 elongate and prfefrontals much longer than broad. Ventrals 173 ; 

 sabcaudals 28. Extremity of tail with a compressed horny cap. 

 Colour everywhere blackish ; some brownish shades on the sides 

 near the head ; free edges of ventral and subcaudal shields, and of 

 lateral scales, lighter. 



Total length 445 millim. ; tail 44. 



Vera Cruz, Mexico. 



7. Atractus peruvianus. 



Rabdosoma peruvianum, Jan, Arch. Zool. Anat. Phys. ii. 1862, p. 12, 

 and Icon. Oin. 10, pi. iv. fig. 2 (1866). 



Snout obtuse. Eostral much broader than deep, just visible from 

 above ; internasals small ; prsefrontals not quite as long as broad ; 

 frontal small, as long as broad, as long as the praefrontals, much 

 shorter than the parietals ; loreal at least twice as long as deep ; 

 two postoculars : temporals 1+2; six upper labials, third and 

 fourth entering the eye ; four lower labials in contact with the 

 single pair of chin-shields, which are moderately large and separated 

 from the symphysial. Scales in 17 rows. Ventrals 140 ; anal 

 entire ; subcaudals 31. Brown above, with five longitudinal series 

 of black spots ; ventrals black, with a white spot at the outer end ; 

 lower surface of tail white, spotted with black. 



Total length 280 millim. ; tail 40. 



Peru. 



8. Atractus guentheri. 



Rhabdosoma maculatum, part., Giinth. Cat. p. 241 (1858). 

 Geophis guentheri, Wv^herer, Proc. Zool. Soc. 186], p. 115, pi. xix. 



fig. 1 ; Gunth. Zool. Rec. 1865, p. 151. 

 Eabdosoma univittatum, Jan, Arch. Zool. Anat. Phys. ii. 1862, 



p. 15, and Icon. Gen. 11, pi. ii. fig. 2 (1865). 



Snout rounded. Eostral small, broader than deep, just visible 

 ■from above ; internasals very small ; prsefrontals broader than long ; 

 frontal a little broader than long (or as long as broad), as long as 



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