CHELONID^. 41 



A. Species founded on the skull. 



Argillochelys, sp. a. 



Imperfectly known, but apparently closely allied to the next 

 species, with which it may prove identical. The rami of the 

 mandible are much less divergent than in species b. 



Hab. Europe (England). 



R. 1447. The nearly entire mandible ; from the Middle Eocene of 

 Bracklesham, Sussex. The total length is 0,069 (2-73 

 inches), and the length of the symphysis 0,023 (0'9 inch). 

 This specimen closely resembles the mandible of the 

 largest skull of A. antiqua. No history. 



R. 1447 a. The symphysis of a larger mandible of similar type. 

 The general contour of this specimen is very similar to 

 that of the mandible of Chelone mydas, but the position of 

 the ridge is different. No history. 



Argillochelys antiqua (Konig 1 ). 



Syn. Chelone antiqua, Konig 2 . 



Chelone breviceps, Owen 3 (in parte). 

 Puppigerus breviceps, Cope 4 (in parte). 



Skull of moderate width, vaulted, and without a sharp descent of 

 the facial profile in the orbital region, Handible comparatively 

 narrow. The occipital shield may either completely divide the 

 paroccipitals, when the interparietal shield is short, without a pos- 

 terior re-entering angle ; or may be pushed completely back to the 

 supraoccipital spine, when the interparietal becomes longer and has 

 a posterior re-entering angle. 



It is probable that either the shells entered under the head of 

 A. subcristata or those mentioned as A. conveooa are referable to the 

 present form, but there are at present no means of connecting them 

 with the skulls. The shells referred by Owen to the present species 

 are entered below as Lytoloma planimentum. 



The rugose character of the cranial bones in the type appears to 

 be due to erosion. 



Hab. Europe (England). 



1 Icones Fossiliirai Sectiles, pi. xviii. fig. 238 (1825). — Chelone. 



- Loc. cit. 3 Kep. Brit. Assoc, for 1841, p. 178 (1842). 



4 Trans. Amer. Phil. Soc. vol. xiv. pt. i. p. 235 (1870). 



