260 



NATURAL HISTORY. 



The Atlantic species of the Loggerhead does not appear to extend into the Indian Ocean ; and 

 a single-clawed, long, fore-limbed kind exists there. It is the Indian Loggerhead. The shell is never 

 much over two feet in length, and the flesh is not eaten, except by the natives of the coasts of the Bay 

 of Bengal, of Malabar, and the Philippines. 



The last genus to be noticed is that of the Leather-back Turtles, whose carapace is not covered 

 with scales of shell, but with a dense coriaceous skin. These Turtles make a roaring noise under 

 certain circximstances, and hence have been included in the genus Sphargis.* They have large fore limbs 

 and smaller hind ones, and there are no nails. The jaws are dentilated, and the skin of the back is in. 

 longitudinal ridges. They grow to a great size, and inhabit the Atlantic and the Mediterranean, and 



HAWK'S BILL TURTLE. 



have been cast on English coasts, having wandered to the north of their usual limits ; moreover, they 

 are found in the temperate zones of all the great oceans. The Sphargis' shell has seven long projecting 

 ridges along it, separated by grooves, and the skin is smooth in adults, but tubercular in young ones. 

 The fore and hind extremities are well developed, and the digits are exceedingly long and form 

 admirable paddles. 



The most important points in the anatomy of the Turtles have been noticed in describing that 

 the Tortoise, and it is only necessary to remark on their great tenacity of life, the great independence 

 of their muscular system, so far as the nervous centres are concerned, and the long-continued energy of 

 their heart after its removal from the body. 



THE EXTINCT CHELONIANS. 



The Chelonians are a very ancient order, and their remains have been found fossilised, especially 

 the limb bones and the carapace and plastron, these being often marked with the impressions of the 

 tortoiseshell plates. 



There are some impressions of feet which have been attributed to the Chelonians in the Trias of 

 Scotland, but it is very doubtful whether they can be referred to them. The first definite evidence 

 of their former existence, is in the Oolitic age. In Europe they have been discovered in the Stonesfield 

 slate, in the lithographic slate of Ciron, in the Portland stone, and in the Purbeck strata. The Marine 

 Turtles are represented in the Portland stone by Chelone planiceps, and two singularly-marked genera, 

 Tretosternon and Pleurosternon (Owen), were discovered in the Purbeck. Probably they are allied t 

 Trionyx. One of tha Purbeck fossil Chelonians belonging to the genus Pleurosternon was believed by 



* Spharyis coriacea, nap<xyie, to roar loudly. 



