184 DE. C. W. AjSDEEWS ON LOWEE MIOCENE [June 1914, 



anterior prolongation of the second neural. This has short postero- 

 lateral borders for union with the second costals ; while, owing to 

 the asymmetry above noted, the right antero-lateral border fo~ 

 the first costal is much longer than the left. Neurals 3 to 7 are 

 hexagonal, the postero-lateral borders being the shortest. The 

 eighth is small, and is longer than broad ; it nearly, or perhaps 

 completely, separates the inner ends of the seventh costals ; but 

 whether it extended at all between the eighth costals cannot be 

 seen. 



The first costal is the largest, and widens out to a considerable 

 extent towards its outer end, although, owing to the large size of the 

 nuchal, to a less degree than in the recent members of the genus. 

 The fourth costal is the narrowest, and is almost of the same width 

 throughout. The seventh costals, as noted above, are probably 

 completely separated by the last neural, while the eighth meet in 

 the middle line and together form the slightly concave posterior 

 border of the shell. The ribs were very thin, and where fused with 

 the costal plates form no noticeable prominence ; their thin free 

 outer ends are broken, but (even when complete) probably did not 

 project beyond the edge of the carapace. 



The sculpture consists of numerous tubercles, which, on the 

 costals, tend to fuse into ridges running for the most part parallel 

 to the edge of the plates, and are best developed near the edge 

 of the shell. The sculpture of the neurals is less distinct, but here 

 also the tubercles tend to form ridges, which in this case are more 

 irregularly arranged. (See PL XXVII, figs. 2 & 3.) 



This specimen was at first regarded as a species of Trionyx, but 

 it is distinguished from members of that genus hj (1) the general 

 outline of the shell, particularly of the posterior border, (2) the 

 form of the nuchal bone, and (3) the nature of the sculpture. 

 In all these points, and in its structure generally, it agrees very 

 well with the two recent species of Cycloderma (C. frenatum 

 Peters, from the Zambesi and the Congo, and C. auhryi A. Dum., 

 from the Gaboon and the Ogowe). On the other hand, it is 

 distinguished from these species by the larger nuchal and the con- 

 sequently smaller first costal; and in the arrangement of the 

 neurals, even if the asymmetry of the anterior two is regarded as 

 an individual peculiarity, there are many differences in detail. 

 It is proposed, therefore, to make this specimen the type of a new 

 species, for which the name Cycloderma victories, sp. nov., is 

 proposed. 



The dimensions (in centimetres) of this specimen are : — 



Length of shell in the middle line 34*3 



Length of nuchal in the middle line (approximate) . . . 4*4 



Width of michal 1 6'8 



Greatest width of shell 307 



The only other portion of the shell of this Chelonian that is 

 preserved is a plate of the plastron (hyo-hypoplastron) of a young 





