24 
Dr. Gray’s Obfervations on the Clafs of 
Whether venomous Serpents can be, with certainty, diftin- 
guifhed from others, and if fo, how they are to be known, is 
what I mean to confider in this Paper ; in doing which I fhall 
examine, firft, how far they may be diftinguilhed by any ex- 
ternal characters ; fecondly, fuppofing the venomous fangs to 
be the only certain criterion, how thofe fangs are to be diftin- 
guilhed from common teeth. 
Though Serpents, by their internal organization, naturally 
belong to the third clafs of the animal kingdom, they are, in 
their external form, more fimple than moft of the animals 
belonging to the three inferior claffes ; their external characters 
muft confequently be very few. I fhall firft examine thofe of 
the head ; and, as all venomous Serpents (fo far as our prefent 
experience extends) are contained in the three firft of Lin- 
naeus’s genera, I (hall, at prelent, confider only thofe three. 
In the firft genus, Crotalus, the head is broader than the 
neck, deprefled or flat at top, and covered with fmall fcales. 
Thefe three characters are particularly obfervable in the three 
intermediate fpecies horridus, Dryinas, and Duriffus. In the 
miliarius the fcales of the head are rather larger than in the 
others. The mutus I have never feen ; but it certainly fhould 
not be placed among the Crotali 
As all the fpecies of this genus are venomous, one is natu- 
rally led, by the examination of it, to confider the fore- 
' mentioned characters as being, in lome meafure, proper to 
venomous ferpents. In order to fee how far they are fo, I (hall, 
for the prefent, pafs over the next genus, Boa, and confider 
# 'Linnjeus’s reafon for not placing it among the Boa? feems to have been, 
that he fuppofed none of them were venomous. He appears, however, to have 
had his doubts about the contortrix* I have examined it, and am convinced it is 
venomous. 
that 
