286 TEETIAET VEETEBRATA OF THE FATtlM. 



In the plastron the differences between the two species are considerable. Thus 

 in the present species the length of the bridge is about half the length of the plastron 

 in the middle line, in T. ammon it is usually less. In consequence of this the 

 anterior and posterior lobes of the plastron, particularly the former, are relatively 

 shorter. The median portions of the epiplastrals {Ep.p.) are produced forwards into 

 a pointed anterior projection ; in T. ammon, when this projection is present at all, 

 it is truncated. The posterior lobe of the plastron narrows more towards its distal 

 end, and the anal region is scarcely at all marked off by the notch or groove which is 

 so strongly defined in T. ammon. Lastly, the groove between the femoral (fem.) and 

 anal {an.) shields slopes more backwards. It may be added that the whole shell 

 appears to have been less solidly built than in T. ammon. This species is named 

 after Mr. H. J. L. Beadnell, by whom the type specimen was found. 



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



C. 8773. Shell of which the carapace is somewhat imperfect. Type specimen described and figured 

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



Length of carapace in middle line 75-1 



„ plastron in middle line 66-4 



,, „ to end of xiphiplastra 71'6 



Width of anterior lobe .... 33 app. 



Length of anterior lobe 18 app. 



Width of posterior lobe .... . . 32-5 



Length of posterior lobe ... 21 app. 



„ bridge .... ... 33 



Height of sheU 35 app. 



Testudo isis, sp. 



nov. 



Type Specimen. — An imperfect shell, wanting the posterior marginals ; Geological 

 Museum, Cairo. 



This species is founded on a comparatively small rounded shell in which the growth- 

 lines of the bones are strongly marked, forming in places {e. g. on the costals) 

 prominent ridges. The areas covered by the vertebral shields are not inflated and 

 pass smoothly into the costal region. The neural bones are all hexagonal, with the 

 antero-lateral sides the shortest. There is a very narrow nuchal shield. 



The anterior end of the plastron is rounded and upturned, but is not greatly 

 thickened as is the case in the carapace of the female of T. ammon (see Plate XXIV.). 

 The posterior end of the plastron forms a wide open notch ; the areas covered by the 

 anals are sharply separated from the region in front. 



The presence of the strongly marked growth-lines probably indicates that this is 

 a young animal, but the fact that all the neurals are hexagonal seems to exclude 



