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CHECKLIST OF THE SNAKES OF MEXICO
Genus

BOTHROPS

Wagler

;

179

'-

Maslin,
1S24, p. 50.
Bothrops Wagler, in Spix, Serpentum Brasiliensium
Copeia, 1942, No. 1, pp. 18-20 (segregation of Trimercsurus)
Bothriechis Peters, Monatsb. Akad. Wiss. Berlin, 1859, p. 278 (type, B. nigro.

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.,

viridis Peters).
Teleuraspis Cope, Proc. Acad. Nat. Sci. Philadelphia, 1859, p. 338 (type,Trigonocephalus schlegelii Berthold).
Thamnocenchris Salvin, Proc. Zool. Soc. London, 18G0, p. 459 (type, T. aurifer

Salvin).

Porthidhim Cope, Proc. Acad. Nat.

Sci.

Philadelphia, 1871,

cephalus Junsbergii Schlegel).
Opliryacus Cope, U. S. Nat. Miis. Bull. 32, 1887,

p.

p.

207

(tyije,

Trigono-

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).

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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-

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curring in Mexico.KEY TO MEXICAN FORMS OF BOTHROPS
1.

2.

3.

4.

5.

6.

Supraocular produced as a soft, hornlike scute
2
3
Supraocular flat
melanurus
Subcaudals entire
undulatus
Subcaudals divided
Supraocular bordered laterally by two or three enlarged, hornlike scales
schlegelii
subcaudals entire; arboreal; greenish
4
Supraocular not bordered by hornlike scales
Snout produced, turned up
5
Snout not noticeablyturned up
7
nasutus
Rostral about twice as high as wide
6
Rostral no more than one and one-half times as high as wide
Bands on body not distinctly paired two lower preoculars small, subequal, excluded from border of orbit; scale rows 21 in front of
yucatanicus
anus
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*' In view of Malcolm Smith's comments (Copeia, 1942, p. 2.56) upon the variation in a
character stressed by Maslin in his recentsegregation 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
This uncertainty regarding the definition of all generic groups in the Americas has
not.
prevented us fromsplitting part of them from "Bothrops." Since the group is now being
In the meantime
studied by others, no doubt all the genera will be satisfactorily defined.
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
This, of course, does not obviate the possibility that oneor
smaller group than now.
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.
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BULLETIN

180187,

UNITED STATES NATIONAL MUSEUM

Bands on body paired, each half \Yell defined and usually separated
medially from its mate; middle preocular considerably larger than
lower, broadly in contact with border of orbit scale rows usually 19
dunni
in front of anus
;

8
Subcaudals single
atrox asper
Subcaudals double
9
Scales in 23 rows or more
10
Scales in 21 rows or less size smaller
Nasal incontact with rostral, not over two, and as few as no scales
whatever, bordering nasorostral contact above or below lower border of postocular stripe usually involving only posterior temporal
mexicanus
of lower row
Nasal separated from rostral by a row of three small scales lower border of postocular stripe involving two to four posterior temporals of
nummifer
lower row
Width of a supraocular about...