CHECKLIST OF THE SNAKES OF MEXICO 177 



Range. — In America, the Pacific coast and Islands from the gulf 

 of California to Ecuador (recorded in Mexico from the states of 

 Colima, Guerrero, Jalisco, Nayarit, Sinaloa, and Sonora, and the 

 Islands of Maria Magdalena, Santa Margarita, and Espiritu Santo) . 



Family CROTALIDAE Gray 



Crotalidae Gray, Ann. Thilos., 1825, p. 204. 

 Type. — Crotalus Linnaeus. 



Genus AGKISTRODON Beauvois 



Affkistrodon Beauvois, Trans. Amer. Philos. Soc, vol. 4, 1799, p. 381. 



Genotype. — Cenchris mokeson (Daudin). 



Range. — Central and eastern United States southward to Nica- 

 ragua; Asia. 



Species. — Thi-ee species {moheson, piscivorus, and Jjilineatus) aro 

 known from the Americas {mokeson with four subspecies, pisclvorus 

 with two) ; nine are known from the Old World. Three forms prob- 

 ably occur in Mexico, although only one is definitely known. 



KEY TO MEXICAN FORMS OF AGKISTRODON " 



1. Scale rows 25; loreal absent piscivorus leucostomus 



Scale rows 23 ; loreal present 2 



2. A prominent light line extending posteriorly from rostral over eye to 



temporal region ; ventrals 129 to 144, caudals 59 to 68, in 23 speci- 

 mens bilineatus 



No light line as described ; ventrals 150 to 153, caudals 52 to 59 in known 

 (5) specimens mokeson pictigaster 



AGKISTRODON BILINEATUS GUnther ^ 



Anolstrodon bilineatus Gxjnther, Ann. Mag. Nat. Hist., ser. 3, vol. 12, 1863, p. 364; 

 Biologia Centrali-Americana, Rept. 1895, p. 186, pi. 58, figs. A, B. — Mocquabd, 

 Mission sclentifique au Mexique et dans I'Am^rique centrale, Rept., livr. 17, 



contained various species in addition to these. Although no type was designated or In- 

 dicated for Hydrophis, the fact that it does not include the type of Hydrus malies impos- 

 sible synonymizing it with the latter (except on zoological grounds, whicli are lacking). 



Tlie use of the name Pelamis is perliaps open to some question, the difference of opinion 

 again involving definition of "substitution." As Stejneger pointed out, in proposing the 

 name Pelamis Daudin states that the name is a substitute for Hydrophis, but likewise 

 Latreille states that his Hydrophis is a substitute for Hydrus. In our opinion, Daudin's 

 mere statement cannot be accepted as fact, any more than can Latreille's, for Daudin's 

 genus is not exactly the same as Latreille's, since it includes yranulatus, a name not 

 placed in Hydrophis by Latreille. 



The first genotype chosen was platurus, type of Pelamis, designated in 1825 by Gray 

 (loc. cit.). If it Is reasoned that Pelamis is a straight substitute for Hydrophis, then its 

 type, since it was chosen first, becomes the type of Hydrophis. 



If, however, Pelamis is reasoned not a simple substitute for Hydrophis, then Pelamis, 

 type platurus, remains acceptable. In this case the name Hydrophis also remains accept- 

 able, its type fasciatus, designated by Smith (op. cit.). This is the arrangement accepted 

 by Malcolm Smith, whom we follow. 



8» From Gloyd and Conant, op. cit., pp. 166-167. 



*• Trigonocephalus Mlineatus (Giinther, 1863) Bocourt, 1882, is a secondary homonym 

 of Tngono'-ephalus bilineatus (Wied, 1825) Schlegel, 1837. For those who suppress sec- 

 ondary homonyms no alternative name is available. 



