404 



ZOOLOGY 



SECT. 



side (Fig. 1008, dg.Jf) : this brings the total number of digits up to 



four, the fifth of the pentadactyle hand alone being unrepresented. 



The simplest type of pelvic girdle is found in Apteryx (Fig. 



1009) and the Tinamus, in which 

 both pubis and ischium are free 

 along 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 this union is ex- 

 tensive, the deep ischiatic notch 

 being replaced by a small fora- 

 men. In the embryonic condition 

 (Fig. 1010) the ilium has a very 

 small pre-acetabular portion, the 

 pubis and ischium are nearly 

 vertical, and there is distinct 

 pectineal process (pp.) retained 

 in Apteryx (Fig. 1009, 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 : in the Emu the posterior end of the pubis 



FIG. 1008. Sterna wilsoni (Tern). 

 Fore-limb of embryo, dg. 1 4, digits ; 

 1m. humerus ; ra. radius ; ul. ulna. 

 (After Leighton.) 



FIG. 1009. Apteryx australis. Left innominate, a. acetabulum ; il. ilium ; is. ischium 

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



gives off a slender process, which extends forwards close to the 

 ventral edge of that bone and probably represents the em-nubis 

 of Reptiles. 



