WII.I.ISTOX: NF.W CRETACEOUS TURTLE. 1 7 



another bone, which agrees better with the epiplastron of Chelone. 

 It is gently convex on the outer, concave on the inner border, taper- 

 ing to a point from the flat blade, and with well-marked longitudinal 

 grooves upon it. It measures i8o mm. in length and has a width on 

 the outer part of nearly 30 mm. If this is the real epiplastron, I do 

 not know what the broad bone is. 



A number of fragments of the hyo- or hypoplastron are present, 

 but, unfortunately, the portion figured cannot be united to the re- 

 mainder, through the loss of intermediate portions. That they all 

 belong to one bone seems evident from the marked peculiarities in 

 the surface, color, and markings. The anterior (?) denticulate mar- 

 gin has a width of 90 mm. ; the posterior hypoplastral border (?) is 

 incomplete, was not more than 60 mm. in width and could not have 

 had a close union with the hypoplastron, if it touched it at all, as the 

 e.xtreme length in this direction is only about 200 mm. The bone is 

 thicker and of firmer texture than is the carapace. The ])osterior 

 end of the xiphiplastron lies under the sacrum. It is only 30 mm. in 

 width, is thin and has four elongated denticulations. The whole 

 structure of the plastron appears to have been something like that 

 in Protospliargis vcroiiciisis. \A'hether the other elements of the 

 plastron were present or not, I cannot now say. 



Systematic position. 



All things considered, I believe that the genus Dcsiiiatoihclxs must 

 be located among the Cryptodira, in a distinct family of Baur's 

 Chclonioidea. But this will necessitate revision of the characters 

 hitherto attributed to both suborder and group. These may best be 

 expressed by giving the characters in detail, as Baur* has expressed 

 them, with the emendations shown in italics. 



Cryptodira. 



Free nasals sometiiiies present, a parieto-squamosal arch present or 

 absent; descending process of prefrontals connected with vomer; 

 stapes in an open groove of the quadrate or covered by the (piadrate 

 behind; pterygoids narrow in the middle, without winglike lateral 

 expansions, separating quadrate and basisphenoid; epipterygoid free 

 or not free; dentary bones united. Cervieal vertebnc rarely with 

 stout transverse processes: the posterior cervicals with double or 

 single articular faces; sacral ribs well developed and connected 

 with centrum and neuroids; Pelvis free from i)lastron, and free 

 or not from carapace. Epiplastra in contact with hyoplastra; 

 entoplastron oval, rhomboidal or T-shaped, a more or less complete 

 series of peripheralia more or less connected with the ribs, or free. 



*Note oil the ClassiHcatioii of Ihe Ci-yptodira. Amev. Naturalist, .luly ISSi.-?. p. fi7:i. 



