XIII 



PHYLUM CHORDATA 



551 



of muscular fibres : 

 the spine has a well 

 developed acromion. 

 The coracoid is elon- 

 gated and in some 

 cases bifurcated. The 

 clavicle is long. The 

 pro-coracoid is repre- 

 sented by a separate 

 ossification ; there are 

 rudiments of the 

 sternal end of the 

 coracoid between the 

 clavicle and the first 

 rib. The humerus, 

 radius, and ulna are 

 all elongated, and 

 the ulna is reduced, 

 being sometimes only 

 represented by the 

 proximal end, anky- 

 losed with the radius. 

 A large sesamoid is 

 developed in the 

 tendon of the triceps 

 muscle near the ole- 

 cranon process of the 

 ulna. In the carpus 

 the scaphoid and 

 lunar are united : 

 sometimes also the 

 cuneiform is united 

 with these : the pisi- 

 form is small. There 

 is no centrale. The 

 ungual phalanges are 

 absent in the nail- 

 less digits. The pel- 

 vis is small, and 

 a symphysis pubis is 

 often wanting. The 

 fibula is sometimes 

 well-developed, some- 

 times rudimentary. 

 The tuber calcanei..is 

 a n inwardly curved 

 r^rocess of the calca- 



