NA TVRAL HISTOR Y. 



v hen the creature is grubbing in the wet banks or burrowing, and evidently protects the face and the 

 eyes from injiiry. The nostrils are close to the extremity of the snout. In the lower jaw, or part 



of the beak-like snout, there are some ridges, which mark it cross- 

 wise from the mouth to the outside, and corresponding structures 

 may be noticed in a Duck, their use being to provide grooves or 

 spaces through which water may pour out of the mouth when the 

 creature is feeding on soft mud and wet substances. Inside the 

 mouth there is a pouch in the cheek, one on each side, and this is 

 to retain food. It has four teeth in the upper and four in the 

 lower jaw, but they are horny and made up of tubes ; the front 

 ones are long and narrow, and the others are oblong and oval in 

 form, with a hollow crown. Moreover, the tongue, as in some 

 reptiles, has horny teeth on it. The eyes of the creature are small 

 and brown, and are situated close to the Leak, and they look 

 upwards. The ear is hidden by the fur, but it is none the less 

 sharp of hearing. As may be gleaned from the notice of its habits, 

 the animal has great power of swimming but not much of running, 

 although the limbs are short. The fore-feet have five toes, nearly 

 equal in length, the first being rather the shortest, and all have 

 solid and rounded claws. The toes are webbed, and the fold of 

 skin even extends in front of the claws when swimming is going 

 on, but is folded back in digging. In the hind-feet the web does 

 not extend farther than the base of the claws, and there is a spur 

 on the heel, which is movable and sharp. It is found on the adult 



_ _ males in perfection, and it may be usetul as well as ornamental. 



POKE (A) AND HIND ( B ) FOOT OF THE Qii carefully examining the under and lower part of the body, the 



DUCK-HILLED PLATYPUS. .., J ' 



(After Wa'erhouse.) vaiik or mammary glands are to be seen, and there is no proper 



nipple ; but when suckling, the swelling of the gland produces an 



eminence, which can be grasped by the wide, open, 



and soft beak of the young. 



It was thought that this bird-like creature laid 

 eggs, but the point was not easy to determine. (See 

 Postscript, page 234.) It has a double uterus, leading 

 to the common canal, called urogenital, and this 

 ends in the common outlet. The Ornithorhynchus 

 and Echidna have an arrangement of the bones of 

 the shoulder .and chest, which resembles to a certain 

 extent that of the Lizards and of the Ichthyosaurus, 

 and the annexed engraving will explain the posi- 

 tion of the bones. Indeed, the most important pecu- 

 liarity in the skeleton of the Monotremes is that of 

 the shoulder-girdle and upper part of the chest; for a 

 bone, the merest vestiges of which are noticed in some 

 of the Mammalia, occurs, that is of some importance 

 in the great groups of birds and reptiles, which are 

 lower in the animal scale than the Vertebrata already 

 described. In all the animals described hitherto, and 

 including the Marsupiata, the large arm bone (humerus) 



SHOULDER-GIRDLE AND STERNUM OF 

 THE ECHIDNA. 



(a) T-Bliapcd interclavirle ; (61 Mamibrinm ; fc) Ensiforra end of 



sternum; (d) Cartilages of ribs; (e) Scapula; m Coracoid; (<<) 

 }-l>icoracold. 



is jointed at the shoulder with the blade bone, or 



scapula. The socket in this bone, which receives the 



somewhat ball-shaped top of the humerus, in order to 



permit of very general motion, is a part of the scapula, and is called the glenoid cavity; but 



in the Monotremes a bone called the coracoid joins with the scapula, and forms part of the socket ; 



