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 consider- 

 ation of the nasals, they are seen to he 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 dee[)ly 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 maxillaiies, 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 apes 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, hounded 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 



[73J 



