1890,] HELODERMA SUSPECTUM. 217 



the sharpened edge of the corresponding coracoid. Such a form as 

 Lacerta viridis, according to Mr. T. J. Parker, has in its sternum 

 characters additional to the ones here described, for it will be observed 

 that Heloderma lacks the "small central fontanelle" and the "two 

 slender flattened cornua" which are produced posteriorly. Indeed, 

 this simple type of sternum in our present subject does not seem to 

 agree exactly with any other form in particular. And to satisfy one's 

 self of this fact it is only necessary to compare the description offered 

 above with the figures of reptilian sterna that have been collected 

 together for us by Hoifmann in Bronn's Thier-Reichs (Kept. 18-21 

 Lief., 1881). 



The Skull. — To complete the account of the axial skeleton a con- 

 sideration of this important part of it still remains. The first thing 

 that strikes one upon a general examination of the skull of Heloderma 

 suspectum is what may be characterized as its peculiar solidity, a 

 certain massive compactness. All the bones composing it are stout 

 and strong. This appearance is still further enhauced by the fact 

 that it is thickly studded for the anterior superficies of its roofing 

 bones by the co-ossified dermal tubercles, and some of these may be 

 found over the parietal region. Old oaken chests or various kinds ol 

 heavy furniture leave the same impression upon our minds, when they, 

 too, have certain parts of them studded with round-headed, brass 

 hob-nails. 



Sutural traces can, but with difficulty, be made out in some in- 

 stances, although in the mandible and in most other localities no such 

 obliterations are met with. Except in front, the encephalic casket 

 is well protected by bony walls, and this kind of protection is also 

 nearly as well afforded to the orbits and the rhinal spaces ; the bounding 

 peripheral margins of these latter are quite circular in outline, while 

 the antero-external narial apertures are very much of the same form. 

 The form of the snout is broadly rounded, and the maxillary alveolar 

 margins are strong and horizontally broad, thus creating a substantial 

 base for the besetment of the teeth. Normally, the massive mandi- 

 bular rami do not fuse by ossification at the mandibular symphysis. 



What is one of the most remarkable facts, however, about the 

 skull of this reptile is the now well-known circumstance that its 

 zygomatic arch is almost completely atrophied, and further that by 

 the union of the post- and prefrontal bones, the frontal is most 

 completely prevented from participating in the formation of the 

 orbital periphery. 



In outhne the comparatively large foramen magnum is a transverse 

 ellipse, while the condyle of the occiput below it is reniform in shape 

 and distinctly exhibits throughout life the sutural traces of the bones 

 that enter into its formation. Spacious from side to side, but not 

 lofty, the posterior temporal fossse are much over-arched by the free 

 posterior edge of the parietal bone. Either parotic process is stout, 

 being directed upwards, backwards, and principally outwards, while 

 the various infero-lateral foramina at or near its base are of com- 

 paratively large size : relatively larger, for instance, than we find 

 them in the skull of a big Iguana tuberculata that I have at hand. 



[H] 



