| OCR Text |
Show 216 DR. R. Vi. SHUFELDT O N [Apr. 1, 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 articulated and prominent,Y-shaped, chevron-bones exist throughout nearly the entire series of caudal vertebras. 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. x\s I have already stated above, Heloderma 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 for their articulation upon either side is rather extensive, but the head of the rib dees not bifurcate. Similar ribs characterize each and all of the remaining cervical vertebras from the fourth to the last. They, however, grow graduallylonger 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 hasmapophyses. These latter are long and sweeping, and are preformed entirely iu 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 ribs, 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 vertebras. The first three pairs of lumbar ribs are short in comparison, each rib rarely measuring more in length than a centimetre, 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 represented by a lozenge-shaped plate of cartilage, as is the case iu the vast majority of ordinary lizards. Quite firmly attached to it and overlapping its anterior angle is seen the hinder end of the interclavicle, 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 monopolized by the remaining hasmapophysial facets. Either anterior border is grooved for its entire length to accommodate in articulation |
