270 CLASS XV. 



CuviER left together in a single lai-ge genus, Coluber. The Pythons, 

 large serpents from the Eastern Hemisphere, which correspond to 

 the Boas, it was thought right, notwithstanding the divided caudal 

 scutes, to place in the neighbourhood of these last. Linnjeus was 

 acquainted with only one species of the former, which he had seen 

 in the cabinet of De Geer, {Coluber mohirus^). In this way a 

 large genus or natural family remained, in which modern writers, 

 especially Boie^, and afterwards Wagler, Fitzinger, Dumeril and 

 BiBRON, adopted many more genera, which they distinguished by the 

 form of the head, by the size of the teeth, &c. We shall not record 

 all these genera, but only those which appear to be most natural, 

 and are distinguished in some other respects, as by their peculiar 

 interest or the number of their species. 



Xenodon BoiE, Fitz. (add. Liopliis Wagl.). Head flat, broad. 

 Gape of mouth ample ; upper jaw with apex rounded, obtuse, 

 emarginate, mostly longer than lower. Last tooth or two last of 

 upper jaws longer than the rest, compressed, ensiform. Eyes 

 moderate. Trunk thick, round, or with back carinate and abdomen 

 compressed. Scales smooth. 



Sp. Xenodon severus BoiE, Coluher severus L., Seba Tkesaur. ii. Tab. 24, 

 fig. I, Linn. Afus. Ad. Frid. Tab. 8, fig. i, Brasil, Surinam; — Xenodon 

 Merremii mihi, Coronella Merremii Schleg., Liophis Wagl., Maxim. Pr. z. 

 WiED, A hbild. Liefer, viii. &c. 



Heterodon Beau v., Latr. Rostral scute porrect, erect. Head 

 short, flat. Circle of numerous quadrangular scutes surrounding 

 the eye. Maxillary teeth small, subulate, recurved ; posterior upper 

 larger ; row of palatine teeth produced almost to the extremity of 

 the external pterygoid bones. Scales carinate. Tail short. 



Sp. Heterodon simus Holbk., Coluber simus L., Catesby Carol. II. Tab. 56, 

 HoLBEOOK N. Amer. fferpetol. 1. PL 16, Cuv. R. Ani., ed. ill., Rept. 

 PI. 27, fig. 2 ;— Heterodon platyrhinos HoLBR., Coluber heterodon Daud. 

 Rept. PI. 60, fig. 28, (fig. of head), HoLBR. 1. 1. 11. PI. 11; — Heterodon niger 

 Tboost, Catesby, ii. PI. 44, Holb. ii. PI. 23. This last species is Pelias 



1 Syst. nat. I ed. 12, p. 387, " Simillimiis Boce, sed scuta et sqimmce capitis majores, 

 ut in Coluhris." 



2 H. BoiE in the unpubhshed Erpetologie de Java, of which his brother F. BoiE 

 communicated an extract in Okbn's Isis, 1827, s. 508 — 566. 



