552 JOURNAL, BOMDA Y NATURAL I1IST0RY SOCIETY, Vol. XVI. 



overlap in two directions, viz., from above downwards and below 

 upwards, but the shape of the costals in this genus makes the 

 overlapping from below upwards far the more evident. The 

 relationship of the vertebral and the last row with their contiguous 

 rows remains the same in the whole longtb of the body, but the 

 intermediate rows alter in a remarkable way, peculiar, I believe, to 

 this genus. The intermediate rows, i.e., 2nd from the ventrals to the 

 7th, when looked at in a transverse direction, are seen to be placed 

 one behind the other from below upwards in the front of the body, 

 but this alters, and these rows gradually acquire a contrary relationship 

 which is seen in the middle and posterior parts of the body. The 

 thickened lines in figures 1 and 2 are intended to illustrate this point. 

 Keels. — Carination is indistinct, and confined to a few median rows about 

 the anal region, the keels being nodulated in character. Supracaudals 

 are in even numbers ; four in the middle of the tail. They decrease at 

 each step by the fusion of the two uppermost rows on each side. Ven- 

 trals 1G8-206 rounded ; if the specimen is laid on its back, barely a por- 

 tion of the last costal row can be seen on each side simultaneously. Anal 

 divided. Subcaudals 127-174, divided. Dentition. — Maxiliary teeth 

 12-15, one or two in the middle much enlarged, fang-like, and followed 

 by an interspace, after which the teeth are very small ; one or two posterior 

 grooved fangs, situated below the posterior border of the eye ; mandi- 

 bular teeth increasing in length to the third or fourth, which is very 

 large and fang-like ; the posterior small (Boulenger). Pterygoid about 

 sixteen, subequal, and small. 



ADDENDA. 



This paper was written eighteen months ago since which time I have 

 acquired information which calls for some additions and modifications. 



1. Here I follow Boulenger. All herpetologists have expressed 

 very different views with regard to this snake. The fact is the charac- 

 ters upon which the classification of snakes is based, are very variable 

 in this genus, and it is therefore almost impoj ,~>le to draw hard and 

 fast rules to separate some of the species, and especially this one. 

 I think from the specimens I have examined, it is more than likely that 

 Boulenger's conception of this species will require further modification. 



