Page:EB1911 - Volume 27.djvu/84

Rh “tortoise-shell,” so far as this is not a fraudulent imitation. When heated in oil, or boiled, the shields (which singly are not thick enough to be manufactured into larger articles) can be welded together under pressure and be given any desired shape. The “hawks bill”

. 6.—Hawksbill Turtle (Chelone imbricata).

ranges over all the tropical and sub-tropical seas and scarcely reaches 3 ft. in length, but such a shell yields up to 8 lb of tortoiseshell.

Thalassochelys caretta, the “loggerhead,” has normally five pairs of costal shields, but whilst the number of shields in the genus Chelone is very constant, that of the loggerhead varies individually to an astonishing extent. The greatest number of neurals observed, and counting the nuchal as the first, is 8, and 8 pairs of costal, in all 24; the lowest numbers are 6 neurals with 5 pairs of costals; odd costals are frequent. The most interesting facts are that some of the supernumerary shields are much smaller than the others, sometimes mere vestiges in all stages of gradual suppression, and that the abnormalities are much more common in babies and small specimens than in adults. The importance of these orthogenetic variations has been discussed by H. Gadow in A. Willey's ''Zoolog. Results'', pt. iii. p. 207-222, pls. 24, 25 (Cambridge 1899).

. 7.—Loggerhead (Thalassochelys caretta).

The “loggerhead” is carnivorous, feeding on fish, molluscs and crustaceans, and is not esteemed as food. A great part of the turtle-oil which finds its way into the market is obtained from it; its tortoiseshell is of an inferior quality. Besides all the intertropical seas it inhabits the Mediterranean, and is an accidental visitor of the western coasts of Europe. The old specimen captured on the Dutch coast in 1894 contained the enormous number of 1150 eggs.

Super-family 2. Pleurodira.—The long neck bends laterally and is tucked away between the anterior portion of the carapace and the plastron. The dorsal and ventral ends of the pelvis are anchylosed to the shell. Fresh-water tortoises of South America, Australia, Africa and Madagascar.

. 8.—The Matamata (Chelys fimbriata) with side view of head, and separate view of plastron.

Family 1. Pelomedusidae.—Neck completely retractile. Carapace covered with horny shields, of which the nuchal is wanting. Plastron composed of 11 plates. With 24 marginal and 13 plastral shields,

. 9.—Lower view of Trionyx euphratica.

inclusive of a conspicuous intergular. Sternothaerus in Africa and Madagascar. Pelomedusa galeata in Madagascar and from the Cape to the Sinaitic peninsula. Podocnemis is common in tropical South America, e.g. P. expansa of Brazilian rivers, noteworthy for