ORDER CHELONIA. 



IIII 



agency. Their skulls resemble those of the next group (fig. 1017 bis) in 

 the slight excavation of the palate, and the produced opisthotics. Finally, 

 the Galapagos tortoises, a considerable number of which were found in 

 Albemarle and Abingdon Islands during the voyage of the Challenger, 

 are distinguished by the double gulars and the absence of the nuchal 

 shield. From the Pleistocene of South America, Dr Moreno describes 

 two large tortoises allied to the Galapagos forms ; one of them being- 



Fig. 1017 bis. — Palatal aspect of the cranium of Testudo 7iiicrophyes ; from the Galapagos 

 Islands. Two-thirds natural size, cut, Auditory aperture ; bo, Basioccipital ; 6s, Basisphenoid ; 

 con, Condyle of quadrate ; 7iix, Maxilla ; oc, Occipital condyle ; op, Opisthotic ; pal, Palatine ; 

 pmx, Premaxilla; pt, Pterygoid; qu, Quadrate; squ, Squamosal; sup, Supraoccipital spine; 

 vo, Vomer. 



described as the probable ancestor of T. nigra {elephantopus) of the 

 latter group. The carapace of T. elephantina measures four feet in a 

 straight line. 



Family Chelonid^e. — The last family of the Cryptodira differs 

 from all the preceding in having the limbs modified into more or 

 less complete paddles or flippers (fig. 1018), which in the existing 

 forms have only one or two claws. The carapace is broad and 

 more or less depressed, and is very generally heart-shaped (fig. 

 1 01 8), although in some of the early forms it is rounded at both 

 extremities. The nuchal bone has no costiform process ; there are 

 usually larger or smaller unossified spaces between the costals and 

 marginals of the carapace (fig. 1006), but in very old individuals 

 these may obliterate in some forms ; and the plastron is not articu- 



vol. 11. p 



