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Show 1890.] HELODERMA SUSPECTUM. 219 important structures which are on their way to the rhinal spaces. That is, during life such is the case. Passing next to a consideration of the nasals, they are seen to be fused together in a manner quite similar to that which has just been described for the frontals, and it is only upon the roof of the rhinal spaces that the sutural traces can be made out at all. Laterally, a nasal articulates with the corresponding maxillary and prefrontal; anteriorly the two unite to send forward a process that articulates with the premaxillary in the middle line ; posteriorly the naso-frontal suture is seen to be represented by a deeply zigzagged line ; and, finally, these fused nasals at their antero-inferior surface, mesially, meet the hinder ends of the septomaxillaries. They assist in the formation of the peripheries and upper parts of the external narial apertures. Articulating with the nasals, the vomers, the maxillaries, and the septomaxillaries, the premaxilla presents a strong mid-process in front which is carried backwards as the nasal process. Its alveolar portion is rather broad and commonly bears upon either side four teeth. Behind these, and in the middle line upon the ventral aspect, are seen two small processes placed side by side. The united anterior apex of the vomers just reaches to them. A similar character to this is seen in a skull of Iguana tuberculata at hand, only in it the apices of these two little apophyses have fused together, thus forming a foramen between them. Again viewing the fore part of the skull upon its externo-lateral aspect, we observe that the thickly set, fused osseous dermal tubercles are carried down over the maxillary and jugal bones upon either side. They do not, however, entirely cover the maxillary, for a narrow strip of its externo-alveolar portion is free from them, and this extends from the jugal all the way round to the narial aperture of the same side. As in so many other forms of Lizards, this smooth and narrow surface of the maxillary seen upon its external aspect, bounded below by its free alveolar margin, is characterized by a longitudinal row of some six or seven minute foramina; they pierce the bone opposite the teeth, or in some instances even between them. Either one of the maxillaries articulates with a good many bones ; it articulates with an os transversum, with a palatine, with a jugal, lacrymal, and prefrontal, with a septomaxillary and a premaxillary, with a nasal, and finally it may even come in contact with one of the vomers of the corresponding side. A maxillary forms the outer lateral wall of the nasal fossa, and also a part of the roof of the same cavity. It also, in Heloderma, contributes largely to the formation of the bony part of the roof of the mouth : and here upon its ventral aspect it is somewhat concaved, while along its alveolar edge the row of teeth are found. These latter are grooved in a manner similar to the teeth found in the mandible, notwithstanding the fact that they do not now seem to be intended to conduct a poisonous fluid at the time the reptile inflicts its bite. Septomaxillaries are large and thoroughly ossified. They are in contact with the maxillaries, the premaxillary, the nasals, and the |