Fossil eggs of birds occur in miocene deposits in Auvergne ; and impressions of feathers have been discovered in the pliocene calcareous marls at Montebolca. In pliocene brick-earth de posits in Essex has been found a fossil metatarsal of a swan, as large as, and not distinguishable from, the existing wild swan ; in the pleistocene clay at Lawford a fossil humerus like that of a wild goose. But most of the ornitholites of this recent tertiary period have been discovered in ossiferous caverns. They belong to birds closely resembling the falcon, wood-pigeon, lark, thrush, teal, and a small wader. The writer has received information of skeletons of birds found deeply imbedded in stratified clay at Aberdeen and Peterhead.
The most extraordinary additions to the present class have been obtained from the superficial deposits, turbaries, and caves in New Zealand.* This island is re markable for the absence of abori ginal species of land - mammals, and for the pre sence of a small bird with very ru dimental wings, and the keel-less sternum and loose plumage of the Struthious order, but of a peculiar genus called Ap teryx : the legs are very robust, and have three front toes and a very small back toe. Birds re sembling the Apteryx in the shape of the sternum and bony structure of the pelvis and hind limbs, some retaining also the small back toe, others apparently without it, formerly existed in New Zealand under different specific forms ranging in height from 3 feet to 10 feet. They have been referred by the writer to the genera Dinornis and Palaptcryx. The gigantic species are interesting, as exhibiting birds equal to the formation of tridac tyle impressions as large as those of the Connecticut sandstones, called Ornithichnites (Brontozoum) gigas (fig. 84, r, b). In this cut is given a figure of the leg-bones of Dinornis giganteus (B), in which the tibia (t) measures upwards of a yard in length. In the entire skeleton (A) of another species, the metatarsus is as thick, but only half as long, as in the D. giganteus ; the frame work of the leg is the most massive of any in the class of birds ; the toe-bones almost rival those of the elephant ; whence the name Dinornis clephantopus, given to this species. Several other species of these extinct tridactyle wingless birds have been de termined—e.g., Dinornis ingens, D. struthiordes, D. rheides, D. deoraioides, D. casuarinus, D. robustus, D. crassus, D. gcranoides,
D. curiae. With these remains have been found bones of a bird the size of a swan, but of an extinct genus (Aptornis) ; also those of a large coot (Kotornis Alantdli) which, founded origi nally on fossil remains, was afterwards discovered living in the Middle Island of New Zealand. Two species of Apteryx, not distinguishable from the existing kinds, were contemporaries with the gigantic Dinornis, and the writer has received evi dence that the D. clephantopus afforded food to the natives at probably no very remote period. Some of the smaller kinds of Dinornis may yet be found living on the Middle Island.
In Madagascar portions of metatarsal bones, indicating a three-toed bird (Epiarnis) as large as, but generically distinct from, the Dinornis giganteus, have been discovered in alluvial banks of streams ; and with them entire eggs, measuring from 13 to 14 inches in long diameter. The contents of one of these eggs is computed to equal those of six ostrich eggs, or of one hundred and forty-eight hen's eggs.
In the neighbouring ishind of Mauritius the dodo (Didus ineptus) has been exterminated by man within the period of two centuries ; and in the islands of Bourbon and Rodriguez the " solitaire" (Pezaphaps) has also become extinct. Both these birds had wings too short for flight.
Class IV.—MAMMALIA.
Fossil bones and teeth have been discovered in every intermediate stage of alteration, from their recent state to that of complete petrifaction. Recent bones consist of a soft—com monly called animal or organic—basis, hardened by earthy salts, chiefly phosphate of lime.* Fishes have the smallest proportion, birds the largest proportion, of the earthy matter in their bones. The soft part is chiefly a gelatinous substance.