110 MR. G. A. BOULENGER ON THE OSTEOLOGY OF [Jan. 20, 



With the kind aid of Professor Stewart, I have been able to bring 

 together and compare the following material : — 



H. horridum, Wiegm. 



1. Adult 5 skeleton from Salina Cruz, Mexico, obtained by Dr. 



A. Buller. In the British Museum. 



2. Imperfect skull of a younger (half-grown) specimen from 



Mexico, extracted from an old sl<in. In the British Museum. 



H. suspeetum, Cope. 



1. Adult 2 skeleton. In the College of Surgeons. 



2. Disarticulated skeleton, without the skull, of an adult J . In 



the College of Surgeons. 



3. Right moiety of skull. In the British Museum. 



In the following notes I have limited myself to the skull and 

 vertebral column ^, which have alone yielded specific differences, the 

 other parts of the skeleton of the two species not differing in any 

 important point, so far as I can see. 



Skull. 



The following characters distinguish the skulls of H. horridum 

 and H. suspeetum : — 



In the latter, the oral portion of the prsemaxillary is narrower, 

 and its ascending internarial bar wider, than in the former — this 



Fig. I. 



Prsemaxillai'ies of H. horridum and H. suspeetum. 

 Front view and upper view ; nat. size. 



jnternarial bar measuring, at its narrowest point, one third instead 

 of one fourth or one fifth of the greatest width of the bone. Eight 

 or nine prsemaxillary teeth are present in H. horridum, and only six 

 in H. suspeetum. Dr. Shufeldt, however, represents eight teeth in 

 the latter species ; but his figure, showing ail the teeth as of the 



1 I must, however, remark that the number of phalanges is 2, 3, 4, 5, 3 in 

 the manas, as correctly described by Shufeldt, whose figure, nevertheless, 

 represents only four in the fourth finger, and 2, 3, 4, 5, 4 in the pes. Through 

 terming the fifth metatarsal bone a tarsal, Shufeldt allows Heloderma but three 

 phalanges in the fifth toe. 



