PHILOSOPHY OF ZOOLOGY. 



are five on each foot, armed with strong claws. On the 

 hind-feet of the male, there is a hollow, conical horny pro- 

 cess at the setting on of the heel, which acts as a sheath to 

 an awl-shaped bone. This bone has a narrow slit in the 

 apex, is hollow throughout, and terminates in a flask-shap- 

 ed bag, that rests on the ligaments of the bones of the foot. 

 In the ornithorinchus, it is placed on the external and pos- 

 terior sides of the leg. Sir JOHN JAMISON, by whom this 

 structure of the spur (as it is improperly called,) was first 

 brought into notice, observed, that the bag at the base con- 

 tained a venomous fluid, which, upon the spur being pres- 

 sed, squirted through the tube. His own servant suffered 

 severely from a puncture with this venomous appendix *. 

 The teeth are composed of vertical horny fibres. There 

 are no external ears. The sternum is destitute of the en- 

 siform process. The clavicles are united into a broad bone 

 (which at first might be mistaken for the sternum), emar- 

 ginate at the anterior extremity. The dorsal extremity of 

 the scapula is imperfect, the clavicular edge is expanded, 

 and scarcely touches the sternum. There are vestiges of 

 marsupial bones. 



It is in the reproductive organs, however, that the pecu- 

 liarities of the tribe are conspicuously displayed. The pe- 

 nis gives passage to the semen alone, the urine being pour- 

 ed into the termination of the rectum (. In the female, 

 there are no teats. The ovaria are double. Their surface 

 is more uneven than in the mammalia. The corpora lutea 



* Lin. Trans, xii. p. 584. ; and a notice of some observations by Dr 

 BLAINVILLE, Ann. Phil. x. p. 112. 



) In the ornithorinchus, the serninal urethra terminates in two openings 

 corresponding with the two ora tincse. In the Echidna, the primary orifices 

 are four in number, with a circle of minute ones around each, leading us to 

 expect (if analogy can be trusted) four uteri or oviducts in the female. 



