262 



THE UNIVERSITY SCIENCE BULLETIN. 



In most Theromorpha, and in Diplocaulus, on the other hand, 

 there is no canal, and the foramen is not on the posterior 

 margin, but farther forward, on the flat surface of the scapula. 



It would seem that the form and position occurring in the 

 lizards is the primitive one, since it is the type of both the 

 Temnospondyli and the Cotylosauria. Apparently, the lizard 

 is the only mesozoic or modern tetrapod which has retained 

 this structure. Gunther shows a foramen piercing the scapula 

 of Sphenodon (article not available to the author), but two 

 scapulae at hand show no evidence of it. 



In determining the function of this foramen the writer has 

 dissected four specimens of Crotaphytus collaris. It was seen 

 at once that the foramen was used for the passage of a blood 

 vessel, and was not used by the nervous system. In order to 

 determine the exact relation and identity of this vessel, the 



Fig. 1. Aortic arches and subclavian of Crotaphytus collaris. Br, brachiel artery; 



CC, common carotid artery; C GI, carotid gland: LAo, left aorta; P, pulmonary artery; 



PT, Pulmonary trunk: RAo, right aorta; Sc, subclavian artery; Su, subscapularis artery; 

 V, vertebral trunk : X, Carotid-systemic connection.. 



subclavian and axillary arteries were traced out in detail. This 

 very interesting system in the lizard has been traced out in 

 detail for Psammosaurus griseus by Corti (1853). The writer 

 does not have access to his account. Hoffmann's account in 

 Bronn's Thierreichs is based upon Corti, but is necessarily con- 

 densed. It is not possible, therefore, to compare Crotaphytus 

 with his account. Hoffmann makes no mention of the supra- 

 glenoid canal, from which it seems that it was not observed by 

 Corti. Possibly the canal is not present in Psammosaurus. 



