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Show 1890.] HELODERMA S U S P E C T U M . 205 tongue in many other reptiles, or with such a lizard, as Varanus instance, where the morphology of the structure is essentially very different1. The Teeth.-These appear to be embedded in the thick buccal membrane that overlies both jaws within the oral cavity in the lizard before us, and it is only in the dried skull that we are enabled to satisfactorily study them. In either jaw the curved line of teeth stand in a slit-like groove of the mucous membrane to which we refer, which is continuous all the way round, and, in addition to this, we find the teeth piercing the basic part of this groove and raising a kind of a papilla at the point of each individual puncture. Bocourt has given us excellent figures of the sharp, curved, conical pleurodont teeth of Heloderma (34), and these have been copied by other naturalists ; so it will be quite unnecessary for me to reproduce these now well-known structures here. In a very fine mounted skeleton of a specimen of Heloderma suspectum in the collections of the Smithsonian Institution at Washington, which I have been permitted to study, I find the following to be some of the characters of the teeth of this reptile. From twelve to fourteen of these seem to be about the normal complement that are destined to ornament the mandible, while perhaps a pair more are to be found in the upper jaw. Iu front these teeth are tiny and small; they very considerably increase in size laterally, while posteriorly they are again smaller, especially in the upper jaw. The largest of all are to be found in the middle of the series in the mandible, the smallest in the premaxilla. Contrary to what I have always understood from published descriptions, I find all of the larger teeth, in both jaws, characterized by the peculiar grooving, although it is best marked in the large ones opposite the site of the poison-gland upon either side. Pleurodont to a less distinctive degree than we find in some other Lizards, these poison-fangs are firmly anchored through anchylosis by a broad base to the rather transversely-spreading ramus, in the case of the mandible, while in the case of the maxilla of the skull they are more laterally attached. When, through accident or otherwise, any of these teeth happen to be lost they are quite rapidly reproduced again, as I have seen from my own observation. All curve more or less backwards, and Giinther has said of them that " In the genus Heloderma the teeth are vertically grooved so as to remind us of their structure iu Serpents. The teeth indeed are more grooved than in them, for one vertical groove passes down on the antero-inner side and another on the postero-outer side of each tooth" ('Encycl. Brit.' 9th ed. p. 457). 1 For a good figure of the tongue, hyoidean arches, and associated parts of a Varanus, see Gegenbaur's ' Elements of Comparative Anatomy' (English translation), p. 553, fig. 310 (Lond. 1878). It is very evident that a bifid tongue, as in the case of a short humerus in a Swift and a Humming-bird, is by no means an index that all of the remainder of the structure in the compared forms will be more or less alike, and consequently point to affinities that in reality do not exist. PROC. ZOOL. Soc-1890, No. XV. 15 |