MONOTREMATA. 



367 



cava by a single large vein. The lower jaw 

 articulates with the base of the zygomatic, and 

 not with the tympanic element of the temporal 

 bone, and the cranium articulates by two dis- 

 tinct condyles with the atlas. 



The quadrupeds which combine these essen- 

 tial mammalian characters with the oviparous 

 modifications above-mentioned are peculiar to 

 Australia and Van Dieman's Land ; they form 

 three well-marked species, referable to two 

 distinct genera. One of these genera, called 

 Echidna by Cuvier, is characterized by an 

 elongated slender muzzle, terminated by a 

 small mouth, and containing a long and exten- 

 sible tongue like that of the Ant-eaters. The 

 jaws are edentulous, but the palate is provided 

 with many rows of small, sharp, hard, epidermal 

 spines, which are directed backwards, and the 

 base of the tongue is similarly armed. The 

 feet are short, but remarkably broad and strong, 

 and are each provided with five very long and 

 strong claws. The upper part and sides of the 

 body are defended by spines similar to but 

 larger than those of the hedge-hog. The tail 

 is very short. The genus Echidna contains two 

 species, one ( Ech. hystrix) characterized by a 

 more complete armour of spines, with a scantier 

 admixture of darker coloured hair; the other 

 (Ech. netosa), by being clothed with a greater 

 proportion of lighter coloured hair, which half 

 conceals the spines. These characters are 

 constant in both sexes, and as well marked in 

 the mature as in the young individuals. 



Both species of Echidna are terrestrial and 

 fossorial ; they feed almost exclusively on ants, 

 and abound in certain districts of both Australia 

 and Tasmania, playing there the same part in 

 the economy of Nature which is assigned to 

 the Pangolins (Manis) in Asia and Africa, and 

 to the Ant-eaters ( Myrmecophaga) in South 

 America. 



The Ornithorhynchus the second genus of 

 the Monotrematous order is an aquatic Insec- 

 tivore,* but combines water-snails, worms, and 

 other small Invertebrata with the insects that 

 constitute the staple article of its food. These 

 it obtains, not by its tongue, which is short 

 and inextensible, but by its lips, which are 

 largely developed, and supported by singularly 

 modified intermaxillary and lower maxillary 

 bones ; the whole mouth presenting a close 

 resemblance to the broad and flattened beak of 

 a duck. The similarity is increased by the 

 lateral lamellae of the lower jaw; but both 

 jaws are provided with four horny teeth ; the 

 anterior one on each side, both above and 

 below, is long, narrow, and trenchant ; the 

 posterior one is broad, flat, and shaped like a 

 molar tooth. The feet are short, broad, armed 

 each with five claws, but less robust than in 

 the Echidna. The fore feet have a web, which 



* See No. 541, B. Physiological Series, Museum 

 Royal College of Surgeons, London. " Debris of 

 Insects belonging to a genus of the Nauceridee, 

 which were found in the cheek-pouches of the 

 Ornithorhynchus paradoxus." Mr. Uennett (Zool. 

 Trans. 1834, p. 239) found in the cheek-pouches 

 of the Ornithorhynchus mud and gravel, with frag- 

 ments of insects and shell-fish. 



not only unites and fills the interspaces of the 

 toes, but extends beyond the extremities of the 

 claws; the web of the hind foot terminates at 

 the base of the claws. With these swimming- 

 feet is associated a strong, broad, horizontally 

 flattened tail, which completes the organic 

 locomotive machinery for the aquatic existence 

 of an air-breathing and warm-blooded quadru- 

 ped. The body is clothed with a dense coat 

 of hair, which consists of a fine fur, intermixed 

 with long, stiff, flattened, and sharp-pointed 

 hairs, that seem to represent the spines of the 

 Echidna. Only one species of Ornithorhynchus 

 is as yet satisfactorily defined ; it occurs in the 

 fresh-water rivers, ponds, and lakes of Australia 

 and Van Dieman's Land. 



As external ears and large eyes would be ill 

 suited to the habits either of a burrowing or a 

 swimming animal, both genera of Monotremes 

 are characterized by the absence of the auricle 

 and the small size of the visual organs. The 

 male in both genera bears a horny pointed spur 

 upon the heel, which is perforated, and trans- 

 mits into the wound it inflicts the secretion of 

 a peculiar gland. This singular repetition of 

 an offensive mechanism, which, prior to the 

 discovery of the monotrematous mammals, was 

 known only in certain insects and serpents, 

 completes the anomalous combinations in the 

 external characters of the present order. 



Echidna hi/strix and Ornitliorliynchus para- 

 doxus were first described and figured by Dr. 

 Shaw; the former as early as the year 1792 in 

 the third volume of the Naturalists' Miscellany, 

 under the denomination of Myrmecophaga acu- 

 leata ; the latter in the tenth volume of the 

 same work in the year 1799, by the name of 

 Platypus anatinus. 



In the following year this more extraordinary 

 animal received a further description, together 

 with its present zoological denomination from 

 Professor Blumenbach, in " Voigt's Magazin 

 fiir den neuesten Zustand der Naturkunde, 

 Bd. ii, 1800;" and soon after Sir Everard 

 Home gave an account of some of its ana- 

 tomical peculiarities, which appeared in the 

 Philosophical Transactions for the year 1800. 

 As these observations, however, were limited 

 to the head and beak, they rather tended to 

 perplex than guide the naturalist in assigning 

 the position of the animal in the natural 

 system. 



Professor Blumenbach, in his Elements of 

 Natural History, placed the Ornithorhynchus 

 paradoxus among the Palmata of his mamma- 

 logical system, between the otter and the 

 walruss ; while Dr. Shaw more naturally re- 

 ferred it to the Bruta of Linnaeus ; but being 

 limited to such points of comparison as the exter- 

 nal form alone presented, he merely discerned 

 the affinities of the Platypus and the Echidna 

 to the Myrmecophaga. The real value and 

 extent of these affinities could only be deter- 

 mined by a deeper insight into their respective 

 organizations. The important memoirs on the 

 anatomical structure of both these animals read 

 before the Royal Society by Sir Everard Home, 

 and published in the Philosophical Transactions 

 for 1802, drew the attention of the scientific 



