216 DR. R. W. SHUFELDT ON [Apr- Ij 



last, to finally disappear altogether, they are seen to be sharp-pointed 

 and stand directly outwards, the first pair being pierced by a foramen 

 upon either side and near the middle of the process. Freely articu- 

 lated and prominentjY-shaped, chevron-bones exist throughout nearly 

 the entire series of cavidal vertebrae. They gradually diminish from 

 first to last, disappearing altogether near the end of the tail, each 

 being directed downwards and backwards and articulating as usual 

 with the postero-inferior rim of the vertebra at its ventral aspect. 



As I have already stated above, lleloderma reproduces that part of 

 its tail that at any time may, through accident, be fractured off. 



A pair of free ribs first occur upon the fourth cervical vertebra ; 

 they are about a centimetre long, slightly curved, flattened, and tipped 

 with cartilage. The facet lor their articulation upon either side is 

 rather extensive, but the head of the rib does not bifurcate. Similar 

 ribs characterize each and all of the remaining cervical vertebrfe from 

 the fourth to the last. Tiiey, however, grow gradually longer and more 

 cylindrical ; indeed, they simply intergrade in form imperceptibly 

 into the thoracic series of the beautiful, strong, and curved ribs that 

 are possessed by this lizard. Passing to the dorsal series we find 

 that it is only the four leading anterior pairs that are connected with 

 the sternum through the intervention of hsemapophyses. These 

 latter are long and sweeping, and are preformed entirely in cartilage. 

 The shortest pair are the anterior ones, the longest the posterior ; the 

 two mid pairs being regularly intermediate in their lengths, and for 

 comparison we find the hinder pair about one third longer than the 

 first pair. They articulate in little pit-like facets that are situated 

 at nearly equal distances apart on the posterior borders of the sternum. 

 The articular facets for the heads of the long hinder pair are 

 found side by side occupying the apex of the postero-mesial extremity 

 of the sternum. Pointed cartilaginous tips, ranging in length from 

 eight to two millimetres, embellish the free extremities of all of the 

 remaining dorsal rii)S, from the fifth to the twenty-second inclusive. 

 These ribs are beautifully and regularly curved ; their vertebral heads 

 are rather large and are non-bifurcated, while their bodies are subcylin- 

 drical in form. The longest pairs are found upon the 13th and 14th 

 dorsal vertebrae. The first three pairs of lumbar ribs are short in 

 comparison, each rib rarely measuring more in length than a centi- 

 metre, while the pair upon the fourth lumbar vertebra are rudimentary, 

 and the last lumbar is entirely without them. Cartilaginous tips 

 seem to be absent from the ends of these ultimate riblets of the 

 series, a fact worthy of notice. 



Heloderma possesses a comparatively small sternum, it being re- 

 presented by a lozenge-shaped plate of cartilage, as is the case in the 

 vast majority of ordinary lizards. Quite firmly attached to it and 

 overlapping its anterior angle is seen the hinder end of the inter- 

 clavicle, the latter being situated ventrad. Its mesio-posterior angle 

 is occupied by two facets for a pair of the costal ribs, as already 

 pointed out, while the contiguous borders to this angle are mono- 

 polized by tlie remaining hsemapophysial facets. Either anterior 

 border is grooved for its entire length to accommodate in articulation 



