DICYNODON, Ow.—In 1844 Mr. Andrew G. Bain, who had been engaged in the construction of military roads in the colony of the Cape of Good Hope, discovered, in the tract of country extending northwards from the county of Albany, about 450 miles east of Cape Town, several nodules or lumps of a kind of sandstone, which, when broken, displayed in most instances evidences of fossil bones, and usually of a skull with two large projecting teeth. Accordingly these evi dences of ancient animal life in South Africa were first notified to English geologists by Mr. Bain under the name of "Biden tals ;" and the specimens transmitted by him were submitted to the writer for examination. The results of the comparisons thereupon instituted went to show that there had formerly existed in South Africa, and from geological evidence, probably, in a great lake or inland sea, since converted into dry land, a race of reptilian animals presenting in the construction of their skull (fig. 73) characters of the crocodile, the tortoise, and the lizard, coupled with the presence of a pair of huge sharp-pointed tusks, growing downwards, one from each side of the upper jaw, like the tusks of the mammalian morse (Trichecus). No other kind of teeth were developed in these singular animals : the lower jaw appears to have been armed, as in the tortoise, by a trenchant sheath of horn.
The vertebra., by the hollowness of the co-adapted articular surfaces, indicate these reptiles to have been good swimmers, and probably to have habitually existed in water ; but the construction of the bony passages of the nostrils proves that they must have come to the surface to breath air. The pelvis consists of a sacrum composed of 5 confluent vertebra, with very broad iliac bones, and thick and strong ischial and pubic lmnes.
Some extinct plants allied to the Lepidodendron, with other fossils, render it probable that the sandstones containing the dicynodont reptiles were of the same geological age as those that have revealed the remains of the Rhynchosaurs and Labyrinthodonts in Europe.
The generic name Dicynodon is from the Greek words sig nifying "two tusks or canine teeth." Four species of this genus, having a rounded profile and less strongly ridged maxillaries, have been demonstrated from the fossils trans mitted by Mr. Bain.
Sp. Dicynodon lacerticeps, Ow..—This species is founded on a skull six inches in length, of which a reduced figure is given in cut 73, where c shows the canine tusks.
Sp. Dicynodon testudiceps, Ow.—In this species the skull, and the facial part more particularly, is shorter than in D. lacerticeps.
Sp. Dicynodon strigiceps, Ow.—The shortening of the jaws and blunting of the muzzle are carried than extreme in this species, in which the nostrils are situated almost beneath the orbits.
Sp. Dicynodon tigriceps, Skull and tusks of Dicynodon lacerticep.
this species the length of the skull is 20 inches, its breadth across the widest part of the zygomatic arches being 18 inches. It differs from the D. lacerticeps not only in size, but in the relatively larger capacity of the temporal fossie, and smaller size of the orbits. These cavities in D. lacerticcps occupy the middle third of the skull, but in D. tigriceps are wholly in the anterior half of the skull. The profile of the skull in D. lacer ticeps begins to slope or curve down from a line parallel with the back part of the orbits, but in D. tigriceps it does not begin to bend down until in advance of the orbits.