Popular Science Monthly/Volume 17/October 1880/The Australian Ornithorhynchus
|THE AUSTRALIAN ORNITHORHYNCHUS.|
LIKE most other animals of Australia and the neighboring islands, the ornithorhynchus presents some strange peculiarities of structure and habit. Its body is flat, about eighteen inches long, its head and mouth are very much like those of the duck, and it has a short, broad, flat tail like that of a beaver. When young, the animal is
naked; the bill is short, and furnished with soft, fleshy borders, which enable the little ones to lay hold of the part on the body of the mother which affords the milk, but which is not pointed out by any teat. The tongue is large, and is likewise adapted to sucking. In the grown
animal the mouth is broadest in front, where it is rounded off; it is hard, and furnished with a porous skin which projects on both sides and runs around the front. Where this skin touches the forehead it forms a broad fold which falls over the brow, and furnishes an excellent protection for the eyes when the animal is digging in the banks of the streams. The nostrils are close to the end of the upper jaw. In the lower jaw, or rather in the lower part of the mouth, are a number of elevations and depressions which run from the interior of the mouth outward through the protecting skin, and serve, like similar features in the duck, to let the water run out of the mouth when the animal is eating in the thin mud. Within the mouth is a pouch in the cheek, which is used as a place for preserving food. Four horny teeth are set in each jaw, of which the front ones are long and narrow, the others oval and hollow-crowned. The eyes are small and brown, set close down by the bill, and look upward. The ear is entirely hidden under the skin, yet the animal hears very well. The fore feet have five long toes, much alike, with thick, rounded claws; the toes are connected by a skin which extends over the claws when the animal is swimming, but is drawn back when it is digging. The skin of the hind footFig. 3.—A, fore foot of the Ornithorhynchus; B, hind foot; a, spur. reaches only to the base of the claws. The males when grown have also a movable, sharp spur on the hind foot. The milk-glands are in the lower part of the body, but are not marked by any teats; the glands swell out on sucking, and the projection thus formed is seized by the broad, soft mouth of the young. It was formerly thought that the ornithorhynchus laid eggs; but it is now known that it brings its young alive into the world from a double uterus through the so-called urogenital canal. The animal chooses its abode in quiet places on rivers and ponds, where the large-leaved water-plants afford it sure concealment, and the steep, muddy banks allow it to dig deep holes, often fifty feet in length. It is extremely shy, cautious, and alert, and generally swims around under the water, only raising its head for breath, but seldom high enough to be shot at. The young, born about the beginning of December, are put by the mother in a nest which she has prepared at the end of the burrow, and has lined with dry grass. They may be caught by digging them out. They do very well in an aquarium, and make comical, playful pets. The grown animals sleep through most of the day rolled up into a ball, but are lively at night. When free, they root for worms in the mud, or catch insects and small animals. They have a peculiar, fishy smell, and are eaten by the natives; but this is no sign that they are good, for the natives have no taste. They belong to the lowest group of the mammalia, the Monotremata, which includes the two genera Ornithorhynchus and Echidna, both these genera exhibit an arrangement of the breast and shoulder-bones which is in a certain degree similar to that of the lizard and the extinct ichthyosaurus. In all the higher mammalia, the humerus is attached to the shoulder in a hollow of the scapula or shoulder-blade; in the ornithorhynchus, the hollow in which the ball of the humerus rests contains a bone connected with the shoulder-blade called the coracoid bone. The breast-bone in the mammalia consists of a broad
bone placed in front in quadrupeds, above the others in man, called the manubrium, and several smaller bones, which reach down to the belly, and have ribs on both sides; while in the other mammalia the manubrium is in contact with the neck-bone, in the ornithorhynchus the two coracoid bones are in contact with the manubrium. Some other bones are found on the breast and neck which are wanting in the other mammalia: first, a T-shaped bone which joins the breast-bone from below, and the cross of which bears at each end a neck-bone that reaches to the shoulder-blade; also, on each side in front of the coracoid bone, a so-called epicoracoid bone reaching to the neck. Some of these bones are found occasionally in birds, reptiles, and amphibia. We meet a few other marks of the reptiles in the ornithorhynchus: for example, some ribs are partly or wholly separated from the spine; the hollow called the acetabulum, in which the thigh-bone is attached to the pelvis, is not perfect; the ear is formed very simply, the auditory canal not being wound spirally, and the outer ear being wanting.