xv.] 1NSECT1VORA. 275 



head for articulation with the glenoid cavity ol the scapula, 

 there is a larger saddle-shaped surface, which articulates by 

 a separate synovial joint with the outer end of the coraco- 

 clavicle. The deltoid ridge is very prominent, joining the 

 inner tuberosity above. From each condyle a slender bony 

 process extends upwards. There is a supracondylar fora- 

 men. The ulna has a greatly developed olecranon, with a 

 narrow keel behind, and expanded laterally at the extremity. 



In the Cape Golden Mole (Chrysochloris) the humerus 

 is much more slender generally than in the true Moles, but 

 the inner condyle is extremely elongated. The olecranon 

 is long, narrow, and incurved. The fore-arm has a third 

 bone, extending from the palmer surface of the carpus 

 almost to the elbow, where it has a free termination. 

 This appears to be an ossification in one of the flexor 

 tendons. 



In the CHIROPTERA both arm and fore -arm are long and 

 slender. The humerus has a slight sigmoid curve, its ulnar 

 tuberosity is large, and there is no supracondylar perfora- 

 tion. The ulna is extremely reduced, only the proximal 

 third being present, and that ankylosed with the radius, which 

 forms almost the whole of the lower articular surface of the 

 elbow-joint. There is a detached sesamoid ossicle near the 

 olecranon, in the tendon of the triceps muscle. 



In the RODENTIA the humerus varies much in its charac- 

 ters. It is long, slender, and straight, with a very slight 

 deltoid ridge, a narrow and laterally compressed inferior 

 end, and without prominent condyles in the Hares and 

 Agutis. But in the Beaver the deltoid and supinator ridges, 

 and the inner condyle, are strongly developed. All inter- 

 mediate conditions occur in different genera. As a general 

 rule there is a large supratrochlear perforation, but no 



supracondylar foramen. In the Coypu (Myopotamus) the 



T 2 



