322 THE ANATOMY OF VEETEBEATED ANIMALS. 



applied to the anterior aperture of the urogenital canal, so 

 as to form a continuous passage for the semen. 



The ova of the female are very large and j)roject from the 

 surface of the ovary, as in the Sauropsida. The mouths of 

 the Fallopian tubes are not fimbriated. There is no vagina 

 distinct from the urogenital chamber. The mammary 

 glands are situated, one upon each side of the middle line, 

 in the hinder part of the abdominal wall. The various 

 ducts of the gland o^jen upon a small area of the integu- 

 ment which is not raised \ip into a teat, so that, in the 

 strict etymological sense of the word, these animals are not 

 Mo.mmalia. The mammary gland is compressed by the 

 panniculus carnosus, and not by any prolongation of the 

 cremaster. 



There is no sufficient evidence of the nature of the foetal 

 appendages ; but the embryo is born in an imperfect con- 

 dition, and may be provided with a knob or caruncle upon 

 the premaxillse, such as is found in the Sauropsida. In the 

 adult the heart exhibits a fossa ovalis. 



Both genera of the OrnithodelpJda are restricted to Aus- 

 tralia, including Tasmania under that name. 



The one of them. Echidna, has the body covered with 

 spines, like a porcupine. It possesses strong digging feet, 

 and a narrow toothless mouth, from which the long tongue, 

 with which it Kcks up the ants wpon which it preys, is 

 protraded. 



The other genus, Ornitliorlnjnclius, has soft fur ; a flattened 

 muzzle resembling the beak of a duck, and covered with a 

 leathery integument ; and clawed, but strongly webbed feet, 

 fitting it for its altogether aquatic mode of life. The Orni- 

 thorhynchus, in fact, frequents fresh water pools and rivers, 

 very much like a water rat, sleeping and breeding in 

 burrows excavated in the bank. 



In these animals the angle of the mandible is not in- 

 flected. They are devoid of any external ear ; and in the 

 males, a kind of spur, which is perforated, and gives exit to 

 the secretion of a gland, is attached to the astragalus. The 

 function of this organ is unknown. In each genus the 



