w rOBK BTATE Ml SET M 



in the middle of the head above : on either side of it are the super- 

 ciliary plat lying immediately above the eye. The pair of 

 plates immediately in front of the vertical are the prefrontals {jpj . 

 in front of these lie the internasak while the plate terminating 

 the muzzle, and lying in front of the prefrontals, is the rostral i 

 The plates behind the snperciliaries and vertical are the occipitals 

 The plates immediately behind the eye are the postoculars, or 

 postorbitalfi in front of the eve are the preoculars, ante- 

 oculars or anteorbital8 (ao), in front of which are the loreals (lo). 



ween the loreal and the rostral, and inclosing the nostril, are 

 the nasal plat The superior labials (7) margin the upper 



jaw; the inferior labials (not marked in figure) margin the lower 

 jaw. The temporal plates lie between the superior labials and the 



[pitals. 



The p] i the under Bide of the body, from the neck to the 



vent, are the abdominal plates, or gastrosteges ; those from the vent 

 to the end of the tail are the subcaudal plates, or nrosteges. The 



U j>Iat> is that immediately anterior to the vent. It may be 

 entire, or divided by a longitudinal parting ; and this difference is of 

 value in the determination of the various snake-, a- will he seen by 

 reference to the artificial key to the genera (p. 3G-i), The term, 



alee in . . . rows," will often be found in the specific description.-, 

 the number <>f rows referred to in such case being the number of 

 longitudinal rows of scales, excluding the abdominal series. K< > 1a d 

 or carinaU scales show a ridge on the median line. 



Variation 



Of late years much attention has been paid by naturalists to the 

 snbject of variation in animals, and certain relations between color 

 variations and geographic distribution seem to be well established. 



Certain Bpecies of snakes show variations in color and color pat- 

 tern t<. a remarkable degree, notable examples of this being the 

 common garter snake and the familiar, though somewhat scarcer, 

 milk Bnake. Prof. EL I). Cope paid particular attention to the vari- 

 ations in these Bpecies, and has discussed the BUbject in a long series 

 of pap era! of which are cited in the accompanying reference 



li-t i p. 357). A- noted earlier in this bulletin (p. 359) the grouping 

 adopted in the present paper follows the views which he advanced 



