280 
TEETIAEY VEETEBEATA OF THE EAY^M. 
In the plastron the difFercnces 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 tlie middle line, in T. ammou it is usually less. In consequence of this the 
anterior and jiosterior lobes of the plastron, particularly the former, are relatively 
.shorter. The median portions of the epiplastrals are produced forwards into 
a ])ointed 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 {fern.) 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 (LTpper 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 GO-4 
,, „ to end of xiphiplastra 71-G 
AVddth of anterior lobe 33 app. 
Length of anterior lobe IS app. 
AVidth of posterior lobe 32-5 
Length of posterior lobe 21 app. 
„ bridge '. 33 
Height of shell 35 app. 
Testiido isisj sp. nov. 
Tyjje 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 {c. g. on the costals) 
])rominent ridges. The areas covered by the vertebral shields are not inflated and 
])ass 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.). 
'J'he 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 fiict that all the neurals arc hexagonal seems to exclude 
