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Show 1890.] HELODERMA S U S P E C T U M . 215 with rounded apex : a thin plate of cartilage, supported by the prevents it from being in contact with the condyle of the occiput during the life of the reptile. The postzygapophyses of this vertebra face almost directly downwards, articulating with the counterfaced prezygapophyses of the third cervical vertebra. From this point, backwards, this is essentially the direction assumed by these articular facets throughout the vertebral series. Passing next to the third vertebra, it is seen to possess a form that, in its main features, agrees with all the other vertebras to the anterior sacral one. It is to be observed, however, that they grow almost imperceptibly wider as they are followed in that direction ; the last lumbar being the widest, and the vertebra now under consideration the narrowest in its transverse diameter. This third cervical vertebra has a peg-like and conspicuous neural spine directed upwards and backwards. This is also characteristic of all the vertebras as far back as to include the second caudal, from whence they gradually become thinner, more lofty and pointed-to again become reduced and gradually disappear as the few terminal joints of the tail are approached, wherein they are quite suppressed. Rudimentary pleurapophysial prominences exist, one upon either side of the fore part of the centrum of the third cervical vertebra, but it does not develop the autogenous hypapophvsis, a character common to some lizards. Indeed there are no hypapophyses present upon the ventral aspects of the centra of the vertebras in Heloderma until we arrive at the first caudal one that bears a chevron-bone. A subcircular intervertebral foramen is found between the vertebras for nearly the entire length of the column, it being intended for the exit of the spinal series of nerves. It is of good size where the brachial plexus comes out, but the largest apertures are those between the last two lumbar vertebras, or where the larger branches of the lumbo-sacral plexus emerge, one upon either side. The centra of the vertebras, including the first caudal, are of average length, rather broad, and flat upon their ventral aspects ; the tail series beyond become gradually narrower, and comparatively longer, as they diminish in size to the ultimate one. Facets for articulation with the heads of the free vertebral pleurapophyses (of those vertebrae that possess them) exist, one upon either side of all the centra at their anterior parts. Choosing at random a dorsal vertebra from the middle of the series, we are to note upon its superior aspect the thin anterior edge of its neural spine and the almost equilateral outline that bounds its nearly horizontal superficies. Apart from their largely developed lateral processes, the two free sacral vertebras agree in the main in their forms with the first caudal vertebra. Their transverse processes are large, rounded, and thick, with dilated outer ends, the bigger pair belonging to the anterior vertebra. These outer extremities, upon either side, seize the ilium between them, the anterior one having the superior hold, the posterior one the under. Slender and rather conspicuous lateral processes also characterize the caudal vertebras; they are probably pleurapophysial developments. Gradually diminishing in size from first to |