190 PLEURODIRA. 
Pecroran ArcH and Fore Lris.—The Pelomeduside and 
Chelydidee are in this respect very similar to the Testudinide, 
except that the humerus is less strongly curved, and the shape of 
the coracoid varies within wider limits; thus in Chelys the latter 
bone widens very considerably towards the epicoracoid cartilage, 
affecting a subtriangular shape very similar so that of the same 
bone in the Land-Tortoises ; in Podocnemis, on the contrary, the 
bone is very narrow and, apart from its being shorter in proportion, 
resembles that of the Chelonide ; the other genera are intermediate 
between the two extremes. The structure of the hand does not 
differ considerably from that of the freshwater Testudinide ; there 
are nine carpal elements, but the radiale and centrale usually fuse, 
and so do the two outer distal carpals in EHmydura; im the latter 
genus and in Podocnemis there is a pair of additional small bones, as 
in many Emyds. The phalanges number 2.3.3.3.3, except in 
Pelomedusa, in which each finger has only two phalanges, the basal 
and the second being fused into one. The genus Carettochelys, as 
far as can be judged from the figure published, appears to have a 
manus very similar to that of the Marine Turtles, the penultimate 
phalanx of the second and third fingers being exceedingly elongate, 
and the third finger is the longest; only the two inner fingers are 
provided with claws. 
Petvis anD Hinp Lims.—All existing Pleurodira agree in having 
the pelvis solidly united with the carapace and the plastron. The 
ilium is expanded at its dorsal extremity, usually subtriangular in 
horizontal section, and, in the adult, bears no trace of sacral attach- 
ment; in the Pelomeduside it is anchylosed to the last and penulti- 
mate costal plates ; in Chelys, Hydromedusa, and Rhinemys to the 
pygal in addition to the two latter; and in Chelodina, Hydraspis, 
Platemys, Emydura, and Elseya to the last costal and the pygal. The 
pubis is anchylosed to the xiphiplastron on a comparatively small 
surface, the extremity of the outer branch, the inner or symphysial 
branch being perfectly free, slender, more or less dilated towards 
the symphysis and directed forwards ; it is nearly parallel with but 
widely separated from the ischium. The latter bone is anchylosed 
to the xiphiplastron by its entire lower surface, which is directed 
obliquely forwards and forms a symphysis with its fellow. With 
the exception of Carettochelys, the hind limbs closely resemble those 
of the freshwater Cryptodira. The tarsus contains two bones in 
the proximal row, a large inner (tibiale+intermedium) and a 
small outer ; the centrale remains distinct in most genera, presenting 
this peculiarity in Chelys that it extends to the inner border of the 
tarsus, separating the inner element of the distal row from that of the 
proximal row ; the centrale fuses with the tibiale and intermedium 
in Chelodina and Elseya, and with the tibiale, the intermedium, and 
the fibulare in one specimen of Hmydura macquarie. Reckoning 
as tarsal the outer bone which is frequently termed the fifth meta- 
tarsal, we have five tarsal bones in the distal row, and the phalanges 
number 2.3.3.3.38, except in Rhinemys, which has only two 
in the fifth toe, and Pelomedusa, where, through fusion, they are 
reduced.to 2.2.2.3.20r2.2.3.3.2. 
