Hay Batrachians and Reptiles of D. C. 



133 



P. Dorsal scales more or less keeled. 

 n. Anal plate divided. 

 o. Scales in less than 18 rows. 



p. Scales in 15 rows. - Storeria ocdpitomaculata, 44. 

 pp. Scales in 17 rows. 



q. Color grass green. - - Opheodrys aestivus, 32. 

 qq. Color brownish. - - Storeria dekayi, 45. 

 oo. Scales in more than 18 rows. 



r. Scales in 19 rows. - . * Regina leberis, 41. 

 rr. Scales in 23 to 29 rows. 

 s. Snout recurved and keeled. 



Heterodon platirhinos, 30. 

 ss. Snout normal, without recurved keel. 

 t. Ventral plates 130 to 160. 

 u. Upper labials 8; preocular 1. 



Natrix sipedon, 39. 

 uu. Upper labials 9; preoculars 2. 



Natrix bisecta, 40. 

 tt. Ventral plates more than 200. 



v. Black, with obscure lighter blotches. 



Callopeltis obsoletus, 35. 

 vv. Red, with dark bordered blotches. 



Callopeltis guttatus, 34. 

 nn. Anal plate not divided. 

 ID. Lateral stripe on 3d and 4th rows of scales. 



Thamnophis sauritus, 42. 

 ww. Lateral stripe on 2d and 3d rows of scales. 



Thamnophis sirtalis, 43. 



Venomous species; a deep pit between the eye and nostril; 



upper jaw in front, with large, erectile, perforated fangs. 



x. Tail short, without a rattle, ending in a horny point. 



Agkistrodon contortrix, 47. 

 xx. Tail provided with a rattle. Crotalus horridus, 48. 



FIG. 2. Topography of a snake, r, rostral plate; , anal plate; 

 tral plates; #, subcaudal plates; 1, upper labials; 2, lower labials; 

 tical plate; 4, occipital plates; 5, postf rental; 7, anteorbitals. 



ver- 



