TESTUDO ISIS.— THALASSOCHELTS LIBTCA. 287 



the possibility of this being the young of T. ammon, and even makes it somewhat 

 doubtful whether it should be referred to the genus Testudo at all. For the present, 

 until further material is available, this species may be called T. isis. 



Form. & Log. — Fluvio-marine beds (Upper Eocene) : north of Birket-el-Qurun. 



C. 8774. Shell, wanting posterior marginals, but otherwise nearly complete and nndistorted. 

 The dimensions (in centimetres) are : — 



Length in middle line of carapace 38 app. 



Extreme width of shell 27 



Length of plastron in middle line 35 



„ „ to end of xiphiplastra 37'4 



Length of bridge 18 



Height of shell 21-4 



Family CHELONID^. 



Genus THALASSOCHELYS, Fitzinger. 

 [Ann. Wien. Mus. i. (1835) p. 121.] 



Eepresented only by imperfect skulls, probably of a single species. 



Thalassochelys libyca, Andrews. 



[Plate XXV. fig. 4.] 

 1901. Thalassochelys libyca, C. W. Andrews, Geol. Mag. [4] vol. viii. p, 441. 



Type Specimen. — The posterior portion of an uncrushed skull (described loc. cit. ; 

 figured PI. XXV. fig. 4) ; Geological Museum, Cairo. 



Known only from imperfect skulls, the characters of which are described below. 



Form. 8f Loc. — Qasr-el-Sagha beds (Middle Eocene) : north of Birket-el-Qurun. 



The specimens of nearly complete skulls of this Chelonian are so much crushed 

 and distorted that they give a very erroneous idea of the general form, and, 

 moreover, they are so much coated with gypsum that the sutures are invisible. 

 For these reasons an imperfect but uncrushed skull has been taken as the type 

 specimen. In this the whole of the anterior portion in front of the epipterygoid 

 [colum£lla cranii) is broken away, but the posterior part is undistorted and in a fair 

 state of preservation. 



In this skull the temporal fossas are completely roofed in, the squamosal apparently 

 meeting the parietal as in the Chelonidse and Sphargidse ; but from the latter group 



