218 



MONOTKEMATA. MAMMALIA. OKXITHORHYXCHID.E. 



examination, several oviparine features will be imme- 

 diately discovered. M. Geoffrey St. Hilaire first gave 

 the name of Monotremata to the small group of non- 

 placental marsupial mammals here associated together, 

 thereby indicating the termination of the urino-genital 

 and intestinal passages by a single cloacal outlet an 

 arrangement also found in birds and reptiles. Equally 

 striking peculiarities affect the skeleton, these being 

 more especially manifest in the presence of two clavicles 

 nearly conjoined, and applied against the upper surface 

 of a single furcular bone ; there are also well-developed 

 coracoid bones, which are articulated to the sternum. 

 In addition to this there are special osseous elements, 

 termed epicoracoids, which are connected to the sternal 

 and furcular bones, the scapulae being likewise attached 

 to the breastbone. In the accompanying woodcut 

 (fig. 93), the furcular bone or episternum presents a 



Sternal apparatus of the Duck-bill (OraitUorhj-nchiis paradoxusj. 



T-shaped outline, with the lateral free ends directed 

 towards the shoulder-blades. It conceals the clavicles, 

 which are slender bones and not united at the mesial 

 line. The epicoracoids are seen interposed on either 

 side of the stem of the furcular bone, resting laterally 

 on the thick coracoids, which latter are articulated to 

 the episternum and manubrial bone of the sternum 

 below and to the scapular above. Another circum- 

 stance worthy of remark is that the bones of the skull 

 become very early consolidated; those of the face 

 being much prolonged forwards and flattened out into 

 -the form of a beak, which is covered by a smooth, 

 naked integument. The jaws are not furnished with 

 teeth ; but their place is supplied by numerous rows of 

 horny dentelations, having their spinous points directed 

 towards the throat, as obtains in the analogous buc- 

 cal papilla? in the mouths of ruminants. They also 

 exist on the tongue in the form of conical papillae. 

 The feet are short, particularly strong, and pentadac- 

 tylous. The Monotremes have small eyes, no external 

 ears, and very short tails. In the male Duck-bill the 

 hind feet are armed with a perforated spur, its channel 

 containing an excretory duct belonging to a special 

 glandular structure placed at the back part of the 

 thigh. This remarkable organ was formerly supposed 

 to be a poison gland ; but there is no good ground for 

 such an opinion. Neither is it merely a weapon of 

 offence and defence ; for then we should probably not 

 have the gland hi connection with the spur, and the 

 females would probably also be similarly armed. We 



have no doubt in our own mind that it is analogous to 

 those supernumerary organs often found in the males 

 of the lower as well as in the higher animals. " Since 

 then," says Professor Owen, " this apparatus forms a 

 sexual character, it may be presumed that its function 

 is connected with that of generation. "Whether the 

 spur be a weapon for combat among the males, or 

 like the spiculum amoris of the snail be used to 

 excite the female, the injected secretion being an addi- 

 tional stimulus ; or whether the spur be mechanically 

 useful in retaining the female during the coitus, are 

 conjectures which must be verified or disproved by 

 actual observation." The females are furnished with 

 mammary glands ; but there are no external teats. 

 The manner in which the function of lactation is per- 

 formed, and many other facts bearing upon the question 

 as to how the offspring are reared, still remain to be 

 explained. 



FAMILY I. ORNITHORHYNCHID^B 



This family is represented by a single species, which 

 is readily distinguished from the members of the suc- 

 ceeding family by its non-fossorial, palmate feet. It is 

 also furnished with eight horny, tooth-like formations 

 regularly disposed, two on either side above and below. 

 The crowns of the anterior pairs are long and thin, 

 those of the posterior set being broader and oval. The 

 snout is prolonged, compressed, broad, and covered 

 by a naked coriaceous integument ; the lower jaw is 

 shorter and narrower than the upper, and marked 

 posteriorly by transverse lines. The tongue is very 

 peculiar; the anterior half or narrow portion being 

 covered with coarse papilla;, whilst the posterior division 

 is broad, slightly overlapping the former, and armed 

 in front by two prominent horny spines. The ornitho- 

 rhynchus is furnished with cheek-pouches. The fur is 

 hairy throughout ; the tail being flattened, broad, and 

 conspicuous. 



THE DUCK-BILL (OnrithorJn/ncfiwi paradoxus), or 

 AUSTRALIAN WATER MOLE Plate 31, fig. 99 is a 

 native of New South Wales and Van Diemen's Land. 

 A full-grown individual varies in length from eighteen 

 to twenty inches, including the tail, which measures 

 about five inches. The fur exhibits a tawny or rufous 

 colour, one or other of these tints prevailing in different 

 varieties. In the young state the skin is entirely 

 destitute of hair, and the jaws are short, soft, and 

 flexible. In the adult the tongue is placed far back, 

 the tip being folly an inch behind the anterior opening 

 of the bill. According to Professor Owen, " the 

 raised posterior lobe of the tongue must impede the 

 passage of unmasticated food to the pharynx, and 

 doubtless tends to direct it on each side into the cheek - 

 pouches, whence the ornithorhynchus may transfer its 

 store at leisure to the molar teeth, and complete its 

 preparation for deglutition. An air-breathing, warm- 

 blooded animal, which obtains its food by the capture 

 of small aquatic animals while submerged, must derive 

 great advantage from the structure which enables it to 

 transfer them quickly to a temporary receptacle, whence 

 they may be extracted and masticated while the animal 

 is floating on the surface or at rest in its burrow." 



