MOODIE: PERMIAN ANPHIBIA. 247 



is in the form of a hook and strongly suggests the hooklike 

 process which is developed in the quadrate of the mosasaurs. 

 This hook and the other elevations on the edge of the bone 

 without doubt served as points of attachment of the deltoid and 

 pectoralis muscles, which were undoubtedly well developed in 

 the species of Eryops. 



The outer surface of the bone is exceedingly rough and there 

 are no less than six distinct elevations on this surface. One 

 of these elevations is a ridge which runs at somewhat of an 

 angle across the posterior edge. There is an indication of a 

 foramen opposite the pit which occurs on one side of the bone, 

 which at first was thought to represent the entepicondylar for- 

 amen. This was such an important matter that the bone was 

 cut through at this point by Mr. Martin and fully demonstrated 

 the total absence of this foramen in the element although there 

 is quite a distinct pit at this point. Cope described such a fora- 

 men in Acheloma, but Case, who has recently examined the 

 type, says the foramen is an accidental opening. Gaudry like- 

 wise described such an opening in Actinodon. 



Measurements of the humerus : 



Length of specimen as preserved 96 mm. 



Estimated length along same line 110 



Width at middle of shaft 50 



Width of top of humerus 90 



Width at lower end 72 



Thickness of head as preserved 23 



Diameter of entepicondylar pit 3 



The element which is here regarded as a radius is very sim- 

 ilar in form to that described by Cope for Eryops mega- 

 cephalus. Its form is well shown in the figure. The lower end 

 is somewhat larger than the upper, which is abraded and 

 broken. Viewed from the lower surface a cross section of the 

 bone shows a semicircular form. It is hour-glass shaped in its 

 entire length, with a shallow groove near the lower end. Both 

 ends of the bone near the articular surfaces are roughened by 

 vascular pits for muscular attachment or for the union of the 

 cartilaginous tips. 



Measurement of radius: 



Actual length of specimen 91 mm. 



Estimated length of specimen 95 



Width of upper end (estimated) 40 



Width^at middle of shaft 24 



Width at lower end 60 



Thickness of base 32 



