xiv.] RODENTIA. 253 



"metacromion." The mesoscapular segment (mss) is a 

 distinct bone. The clavicle (<:/) is long and slender. It has 

 a small piece of cartilage (pc] attached to its inner end. 

 The omosternum (ost) is cartilaginous or partially ossified, 

 and there is a considerable triangular flattened rudiment 

 of the inner end of the coracoid (ec) attached to the pre- 

 sternum. 



In the other Insectivora the general form of the scapula 

 is more normal. In Galeopithecus the coracoid is greatly 

 developed and bifurcated. 



All known members of the order have large clavicles, with 

 the exception of Potamogale, a rare aquatic form from 

 West Africa. 



In the CHIROPTERA the scapula is large, of an oval form, 

 and chiefly formed by the postscapular fossa, the anterior 

 fossa being extremely small. The former is divided into 

 two or three subfossae by ridges. The spine is short and 

 moderately high, with a large and simple acromion. The 

 coracoid is long and curved, often simple (as in Pteropus] 

 sometimes forked (as in Pipistrellus). 



The clavicle is very long and curved. The " mesoscapular 

 segment " on the outer end is soon lost, but the precoracoid 

 ossifies separately. The omosternum is reduced to a 

 cuneiform fibro-cartilage. A rudiment of the sternal end of 

 the coracoid is often present as "a flat, reniform flap of 

 cartilage, feebly ossified by endostosis, wedged in between 

 the clavicle and the first rib " (Parker). 



The RODENTIA offer great diversities in the condition of 

 the shoulder girdle. The scapula is generally high and 

 narrow, and the acromion long. Sometimes the acromio- 

 scapular notch is so deep, that the actual spine only occupies 

 a short space near the suprascapular border, and it is com- 

 pleted by a very long and slender acromion (as in the Coypu, 



