188 APPENDIX F. REPTILES. 



REPTILES. 



BY S. F. BAIED AND C. GIEAED. 



SERPENTS. 



The serpents collected by Captains Marcy and McClellan belong to 

 ten species, distributed into eight genera. Several of these species had 

 previously been received from other sections of the country ; three, 

 however, were first collected during the expedition. All are here 

 figured for the first time, except Ophibolus Sayi, of which a hitherto 

 undescribed variety is represented. 



L CROTALUS, Linn. 



This genus is characterized by its erectile poison fangs, and by 

 having the upper surface of the head covered with small plates resem- 

 bling the scales on the body, and with only a few larger ones in front. 

 There is a deep pit between the eyes and the nostrils. The plates under 

 the tail are undivided, and the tail is terminated by a rattle. Scales 

 carinated. 



1. Crotalus conelttentus, Say. 



Zoology, PL 1. 



Spec. char. — Head subtriangular. Plates on top of head squami- 

 form, irregular, angulated, and imbricated ; scales between supercilia- 

 ries small, numerous, uniform. Four rowes of scales between the sub- 

 orbital series (which only extends to the centre of the orbit) and the 

 labials. Labials 15 or 18, nearly uniform. Dorsal series 27-29. 

 Dorsal blotches quadrate, concave before and behind ; intervals greater 

 behind. Spots transversely quadrate posteriorly, ultimately becoming 

 10 or 12 half rings. Two transverse lines on superciliaries, enclosing 

 about one-third. Stripe from superciliary to angle of jaws, crosses 

 angle of the mouth on the second row above labial. Rostral margined 

 with lighter. 



