TESTUDO ISIS.— TIIALASSOCJIELTS LIBYOA. 
287 
the possibility of this being tlie young of T. ammon, and even makes it somewhat 
doubtful whether it should he 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 undistorted. 
The dimensions (in centimetres) are : — 
Length in middle line o£ 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.] 
Represented only by imperfect skulls, probably of a single species. 
Thalassochelys libyca, Andrews. 
[Plate XXV. fig. 4.] 
1901. Thalassochelys lihyca, C. W. Andrews, Geol. Mag. [4] vol. viii. p. 441. 
Tij'pe Specimen . — The posterior portion of an uncrushed skull (described loc. ext . ; 
figured PI. XXV. fig. 4) ; Geological Museum, Cairo. 
Known only from imperfect skulls, the characters of which are described below. 
Form. ^ 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 
{cohmiella cranii) is broken away, but the posterior part is undistorted and in a fair 
state of preservation. 
In this skull the temporal fossae are completely roofed in, the squamosal apparently 
meeting the parietal as in the Chelonidae and Sphargidae ; but from the latter group 
