490 



CHORD AT A, 



secretes the shell. They have no distinction into Fallopian 

 tube, uterus and vagina, and they open separately into the 

 urogenital sinus. 



Fig. 334. — Ventral View of Pectoral Girdle and 

 Fore-Limb of Ornithorhynchus. {Ad nat.) 



"^ Scapula. 



Coracoid. 



Sternum. ^^"" 



Humerus. 



Radius. 



Ulna. 



3. Cloaca. — The urogenital canal and the alimentary 

 canal have a common passage called the cloaca which opens 

 by a single aperture to the exterior, the cloacal aperture 

 (hence Monotremata). 



Fig. 335. — Pelvis of Ornithorhynchus x \. {Ad nat,) 



Sacrum. Ilium. 



Epipubic. " 



Pubis. 

 Obturator Fora-- 

 men. 

 Ischium. 



Acetabulum. 



A Epipubis. B Ischium. 



A, Ventral view. B, Lateral view. 



4. Skeleton. — Shoulder-girdle has complete precora- 

 coids, coracoids and episternum. The scapula is bent 

 forward and the spine is at the anterior border, not down 

 the middle. 



