1890.] HELODERMA SUSPECTDM. 223 



the vagus and condylar foramina are to be found at their most 

 comnion sites as seen in ordinary Lizards. The anterior margin of 

 the prootic is also notched for the passage of the 5th and 7th nerves, 

 this notch being converted into a foramen by the membrane that 

 helps to enclose the fore part of the cranial casket when the skull is 

 normally complete. The 8th nerve emerges from the internal 

 auditory meatus. 



Next turning to the mandible I would add a few words to what 

 I have already said in reference to the teeth. The ducts which 

 lead from the poison-gland upon either side do not pass directly 

 through the ramus of the jaw to the base of the groove of the tootli 

 to be supplied, as one might naturally suppose. Rather this is the 

 arrangement. Let us choose a large tooth from the middle of the 

 series for an example. In the first place it must be noted that 

 when the grooves upon the tooth are followed down to the base of 

 the tooth it is not at that point that we find the internal foramen 

 that is intended to transmit the poisonous fluid to the groove in 

 question. The external duct enters by means of a foramen directly 

 through the outer bony wall of the ramus. This leads into quite a 

 cavity which exists in the body of the jaw and at the base of the 

 tooth. Now the foramen that leads into the mouth and finally 

 supplies the tooth with the venom makes its entrance, as I have 

 already said, at the base of the structure, but by this I by no means 

 intend to imply that the dental groove leads into this opening. On 

 the other hand it is found exactly opposite the tooth and well 

 towards the mesial plane. It will be seen that the base of the tootli 

 slopes inwards and slightly backwards, and the reverse of this 

 course indicates the direction of the internal division of the fora- 

 minal passage when followed from within outwards. From the 

 structure of these parts, then, I am compelled to infer that the fate 

 of the venom upon being jetted from the gland is this : — it passes 

 directly, though somewhat obliquely, through the body of the 

 mandible, and enters the mouth through the foramen at the extreme 

 baseof the tooth towards the median plane. Theedgesof the tiiickened 

 mucous membrane on either side of the row of teeth form there a 

 longitudinal gutter as it were ; this is flooded full upon the venom 

 being thrown into the buccal cavity, it surrounding the teeth in 

 consequence. Then, simultaneous with this, when the reptile makes 

 its bite, the grooves upon the teeth simply serve as conduits to 

 conduct the venom into the wound. And when one comes to think 

 of it, this IS a very simple arrangement, the more especially so when 

 compared with the more highly perfected poison-fangs of such a 

 reptile as Crotalus. 



Heloderma has a mandible to its skull that seems to be composed 

 of the usual number of bones found in the make-up of lower jaws of 

 all ordinary Lizards. There is a strong well-developed articular, 

 with its large angular process directed posteriorly, and with its 

 articulation for the quadrate, the latter showing two concavities 

 facing upwards, backwards, and inwards. Upon the inner side of 

 the ramus, between the articular and the coronary, there is to be 



16* 



