314 DR. C. W. ANDREWS ON A NEW SPECIliS OF 



relationship, and it is interesting to note that probably the 

 ancestors of the Centetidfe lived in Africa, in early Tertiary times, 

 and it is there also that the Zeuglodonts probably originated. 



CoSMOCHELYS DOLLOi, gen. et sp. nov. 



The .second specimen (E. 4338) now described consists of 

 portions of the centi^al region of a carapace belonging to a 

 Chelonian referable to the so-called Athecpe, to which belong the 

 i-ecent Leathery Turtle, Derinochelys coriacea, and the Tertiary 

 genus Pse2:>hophorns to which the present form seems to be most 

 nearly allied. This specimen Avas presented to the Museum by 

 Sir John Eaglesome, K.C.M.G. Unfortunately, the fragments 

 seem to have been picked up at random, so that much has been 

 lost ; b\it, nevertheless, it has been po.ssible to join a certain 

 number of pieces, which together make up a portion of the 

 carapace measuring about 37 cm. long by 27 cm. wide. On the 

 right side of this the upper jiortions of five ribs are preserved 

 and on the left, three, corresponding to the posterior three on 

 the right side. In the case of these three posterior ribs, the 

 upper portion of their articular ends are preserved, articulating 

 with the neural arches. These bore neural short spines, to tlie 

 upper ends of Avhich the remnants of the disappearing neurals are 

 joined. The whole outer surface of the carapace is covered by a 

 thick armour of epithecal plates, corresponding to the shell of 

 Dermochelys. 



This epithecal shell may be described first. As in Derviochehjs: 

 it consists of several rows of longitudinall}' keeled plates separated 

 by a mosaic of smaller plates without ridges. The keeled plates 

 forming the median dorsal ridge are roughly hexagonal and elon- 

 gated in a, longitudinal direction ; they present much the appear- 

 ance of the neurals of a thecal carapace. The keeled plates of the 

 two upper lateral rows are seen also to be irregularly hexagonal ^ 

 but shorter than those of the median row. Two or three isolated 

 keeled plates (PI. II. fig. 3), to which the outer points of ribs 

 are adherent, are mucli larger than the rest and are nearly 

 quadrate in outline; they were pi'obably near the margin of the 

 carapace and are thinner than the central plates. The exact 

 number of keeled ridges cannot be determined, but there were at 

 least seven. The central part of the carapace preserved shows a 

 median and two lateral i^idges, Avhile the large (? marginal) platen 

 a,bove i-efened to bear another, and others may have been present, 

 since it is unknown how much of the carapace is missing 

 between the outer part of the main fragment and the margin; 

 the distance must have been consirlerable to allow for the 

 narrowing of the broad ribs towards their outer pointed ends. 

 In Devmochelys a median and three lateral I'idges are present, 

 seven in all, but Vtilker * thinks that probably there were- 

 originally nine. 



* Volkev, "Dermochelys coriacea;'' Zoo]. Jalivlniclier (Aiuitoinie). vol. x.wiii. 

 (1913), p, 477. 



