THE SIDE-NECKED TORTOISES 2455 



inhabits both Eastern Africa and Madagascar. The right half of the upper shell of 

 one of the species is represented on p. 2447. 



A remarkable Chelonian (Carettochelys insculpta) from the Fly 

 river, New Guinea, differs from all other members* of the group, in 

 the absence of horny shields on the shell and the conversion of the 

 limbs into paddles, each of which carries but two claws. The neck is not retract- 

 ile. In the carapace there are six very small neural bones, which are not in con- 

 tact with one another, thus allowing each pair of costals to meet in the middle line; 

 and the plastron has only the usual nine bones. A wavy sculpture ornaments the 

 whole of the external surface of the shell, which attains a length of about eighteen 

 inches. The head is large, and the tail relatively short. The species, which rep- 

 resents a separate family (Carettochelyidcz} , is still very imperfectly known, and it 

 has been suggested that it does not belong to this group at all. It is not improba- 

 ble that a Chelonian {Hemichelys) from the Eocene rocks of India indicates a second 

 member of the same family, as its shell was similarly devoid of horny shields. 



Probably the most aberrant members of the whole order were cer- 

 tain gigantic tortoises- (Miolania) from the superficial deposits of 

 Tortoises Australia, characterized by the presence of several pairs of horn-like 



protuberances on the skull, and also 

 by the investment of the tail in a bony sheath, 

 recalling that of the armadillos. Unfortunately, 

 the shell of these strange reptiles is known only 

 by fragments; but, from the conformation of 

 the bones of the feet, we are enabled to say 

 that they were terrestrial, while the structure of 

 the palate indicates that they were herbivor- FRONT VIEW OP SKUU, OF HORNED 

 ous. They clearly constitute a fourth family TORTOISE. 



(Miolaniida] of side-necked tortoises. 



The Secondary rocks of Europe contain the remains of a number of 

 extinct tortoises which may be referred to a fifth family (Plesiocke- 

 Genera lyidce} of the group. While agreeing with the existing Chelyidts in 

 having but nine bones in the plastron, these extinct forms differ by 

 the much greater thickness of their shells, and also by the circumstance that only 

 one of the lower bones of the pelvis is welded to the upper surface of the plastron, 

 whereas in the existing families both are thus united. Abundant in both the 

 Oolitic and Wealden rocks, the majority of these tortoises are referred to the genus 

 Plesiochelys, although some, as the one of which the carapace is represented in the 

 figure on the next page, are separated as Hylcechelys, being distinguished by the enor- 

 mous width of the vertebral shields, in which the breadth may be three times the 

 length. Nothing approaching this conformation is to be met with among living 

 representatives of the order. 



Certain extinct tortoises, such as Pleurosternum from the Purbeck 



Oolite of Swanage, and Baena of the Eocene rocks of the United 

 Chelonians 



States, indicate the existence of an extremely generalized group of 



the order Amphichelydia, presenting many characteristics common to the existing 



