xm 



PHYLUM CHORDATA 



419 



their whole length, as in Dinosaurs. In the Emu and Cassowary 

 the pubis and ischium unite by cartilage or bone at their posterior 

 end with the ilium, and in most Birds the union between the two 

 last is extensive, the deep ischiatic 

 notch being replaced by a small 

 foramen. In the embryonic con- 

 dition (Fig. 1083) the ilium has a 

 very small pre-acetabular portion, 

 the pubis and ischium are nearly 

 vertical, and there is a distinct 

 pectineal process (pp) retained in 

 Apteryx (Fig. 1082, p.) the whole 

 pubis being singularly like that of 

 a Dinosaur. In the Ostrich alone 

 the pubes unite in the middle ventral 

 line to form a symphysis : Rhea 

 presents the unique peculiarity of 

 a dorsal symphysis of the ischia, 

 just below the vertebral column : 



? ,, -n, -, FiQ. 1081. Sterna wilsoni (Tern). 



in tne JLmU tne posterior end OI Fore-limb of embryo, dg. 14, digits ; 



the pubis gives off a slender pro- ^fteXSon.?' radius; uL ulna ' 

 cess, which extends forwards close 



to the ventral edge of that bone and probably represents the 

 epi-pubis of Reptiles. 



The bones of the hind-limb are very uniform throughout the 

 class, but the form of the tarso-metatarsus of Penguins is worthy 



r7 



FIG. 1082. Apteryx australis. Left innominate, a. acetabulum ; H. ilium ;ts. ischium ; 

 P. pectineal process ; pi. pubis. (From Wiedersheim, after Marsh.) 



of notice. It is short and wide, its three constituent metatarsals, 

 though fused, are clearly distinguishable throughout their whole 

 length, and the resemblance to the homologous part in Iguanodon 



