CHECKLIST OF THE SNAKES OF MEXICO 179 



Genus BOTHROPS Wagler '- 



Bothrops Wagler, in Spix, Serpentum Brasiliensium . . ., 1S24, p. 50. — Maslin, 



Copeia, 1942, No. 1, pp. 18-20 (segregation of Trimercsurus) . 

 Bothriechis Peters, Monatsb. Akad. Wiss. Berlin, 1859, p. 278 (type, B. nigro- 



viridis Peters). 

 Teleuraspis Cope, Proc. Acad. Nat. Sci. Philadelphia, 1859, p. 338 (type, Trigono- 



cephalus schlegelii Berthold). 

 Thamnocenchris Salvin, Proc. Zool. Soc. London, 18G0, p. 459 (type, T. aurifer 



Salvin). 

 Porthidhim Cope, Proc. Acad. Nat. Sci. Philadelphia, 1871, p. 207 (tyije, Trigono- 



cephalus Junsbergii Schlegel). 

 Opliryacus Cope, U. S. Nat. Miis. Bull. 32, 1887, p. 88 (type, Trigonocephahis 



undulatus Jan). 

 Thanatophis Posada-Aranga, Bull. Soc. Zool. France, 1889, p. 343 (type, T. torvus 



Posada- Aranga [=5. schlegelii Berthold]). 

 Trimcresuriis Smith (ncc Lacepede), Zoologica, vol. 26, 1941, pp. 61-64 (notes on 



and key to Mexican species). 



Genotype. — Coluber lanceolatiis Lacepede. 



Range. — Tamaulipas and Guerrero, Mexico, southward on both 

 coasts through Peru and Argentina. 



Species. — About 51 species and subspecies in the Americas, 13 oc- 

 curring in Mexico. 



KEY TO MEXICAN FORMS OF BOTHROPS 



1. Supraocular produced as a soft, hornlike scute 2 



Supraocular flat 3 



2. Subcaudals entire melanurus 



Subcaudals divided undulatus 



3. Supraocular bordered laterally by two or three enlarged, hornlike scales ; 



subcaudals entire; arboreal; greenish schlegelii 



Supraocular not bordered by hornlike scales 4 



4. Snout produced, turned up 5 



Snout not noticeably turned up 7 



5. Rostral about twice as high as wide nasutus 



Rostral no more than one and one-half times as high as wide 6 



6. Bands on body not distinctly paired ; two lower preoculars small, sub- 



equal, excluded from border of orbit; scale rows 21 in front of 

 anus yucatanicus 



*' In view of Malcolm Smith's comments (Copeia, 1942, p. 2.56) upon the variation in a 

 character stressed by Maslin in his recent segregation of Bothrops and Trimercsurus, 

 the retention of the former name for American members of the group demands some 

 explanation. Our chief reason is that the American species themselves rather clearly 

 belong to more than one genus ; certain ones of these are easily defined, while others are 

 not. This uncertainty regarding the definition of all generic groups in the Americas has 

 prevented us from splitting part of them from "Bothrops." Since the group is now being 

 studied by others, no doubt all the genera will be satisfactorily defined. In the meantime 

 we rely upon the knowledge that in reality several genera occur in the Americas to justify 

 the use of a name with an American type, granting that Bothrops will be restricted to a 

 smaller group than now. This, of course, does not obviate the possibility that one or 

 more of the American genera may occur in the Eastern Hemisphere and that one of these 

 may be Trimeresitrus. Clearly no disposition can be satisfactory until a thorough study 

 of the group is completed ; and until that time we believe the least disturbing course is to 

 retain Bothrops for American species, Trimercsurus for those of the Eastern Hemisphere. 



