154 PROCEEDINGS OF THE ACADEMY OF [Mar., 



just back of the occipital plates. Often this median prolongation 

 is cut off and surrounded by body color. Usually on the occipital 

 suture and occipitofrontal suture appears a light spot. 



In some of the adults the same schema of coloration obtains as 

 in the young, except that dorsal and lateral spots are less distinct 

 as such and become more transverse areas with light intervals. 

 Furthermore, the supralabials are more prominently spotted in the 

 young. 



Of the 21 specimens of adults, 8 were of the black (niger) type 

 with slaty-gray below. In most of these 8 the gular scales and 

 whole chin except in two become the darkest portion of the whole 

 venter. Of the spotted forms (platyrhinus) , we had a few with the 

 brick-red on the head and neck and somewhat on the body. In the 

 intermediates, the approach to the black phase begins in the head 

 region and the head first becomes black, or it and the neighboring 

 cephalic region. In this process the transverse light intervals 

 remain brightest and persist longest in the tail region. Some of the 

 specimens are almost niger in the cephalic region, but platyrhiyius 

 in the caudal half, or three-quarters niger with the scales of the light 

 intervals of the caudal region with incoming black centres. About 

 7 of the adults were true spotted adders and 6 intermediate. Thus, 

 of the adults we have an almost equal division of 7 spotted, 6 inter- 

 mediates and 8 blacks. Most of our largest specimens were black 

 or fast approaching that stage. The black seems to be an end phase 

 of size or age, possibly not always attained in an individual, but 

 certainly the spotted phase is most prominent in the smaller speci- 

 mens of the collection. Besides, it might be remembered that none 

 of the 16 young were black, but all true spotted forms. 



Dimensions and Variations. — The 16 young vary in length from 

 13.7-19.6 cm., while the adults are from 35-104.2 cm. (1 ft. 2 inches- 

 3 ft. 5 inches). Possibly the species may reach 4 feet in length and 

 a circumference of 6 inches, largest specimen being 5 inches in girth. 

 The gastrosteges range from 120-146, average 130; the urosteges 

 30-59, average 48; the anal is divided, in several with half a gastro- 

 stege ahead; the scale row formula of 18 individuals is 25-25-19, 

 the other formulae being 23-23-17, 24-22-17, 24-24-19, 25-21-19, 

 25-22-21, 25-23-18, 25-23-19, 25-25-18, 25-25-20, 25-25-21, 

 25-25-23, 26-25-21, 27-24-18, 27-25-19, or in the middle of the 

 body from 21-25, exceeding the usual range of the 3 species of 

 Heterodon by the loss of two rows (in 21-rowed condition) or in the 

 cephalic region extending from 23-27, two rows beyond the normal 



