184 A new genus of Serpents, ifc, 



erectOy elato, antice acuto siijpra carinato ; dentibus ditabus Ion" 

 gioribus et simpUcibus in utroqiie latere maxilla sujjerioris : 

 Cauda yj.*' I said that this diagnosis is only j'^rtly correct. 

 The long teeth mentioned here are not two, but four in num- 

 ber : and besides the teeth, the skeleton of the hea d differs iri 

 several particulars from that of the Coluber, And these cha- 

 racters are permanent in three different species, in case we 

 consider Heterodon as a genus j if it form a species of Colu- 

 ber, they must be considered as varieties. 



Desirous to see what occasioned this singular shape of head, 

 and also to convince myself of the absence of the venomous 

 fangs, I dissected several heads; and not only found that the 

 above-mentioned teeth amounted to four, but that the whole 

 bony structure differed from that of the Coluber, 



The dimensions of the different bones which compose the 

 head of the Heterodon differ much from those of the other ge- 

 nera of this order of animals. The following are the compa- 

 rative dimensions of the corresponding parts of the head of a 

 Heterodon of the size of the orte which has been described in 

 this paper, and a Coluber of between six and seven feet long, 



Heterodon. Coluber. 



Tympana - - - - -^^ 



From the extremity of the parietal bone 

 to the extremity of the intermaxillary, 



7_ i 



2 



10 



or the tip of the muzzle 

 Os articulare joined to the os dentale of 



the lower jaw _ _ _ i_L. \^ 



From the tip of the muzzle to the occiput ^ 1^ 

 From the extremities of the posterior os 

 frontis, across the head, giving the 

 breadths of the same - - ^ f 



We see, in these proportions, the remarkable length of the 

 tympana, in proportion to the dimensions of the other bones : 

 they are of the same length of the whole head, from the extre- 

 mity of the parietal bone to the tip of the muzzle, both being 



