Two new Species of Fossil Tortoises. 147 
where the sulci marking their boundaries are well defined. 
The whole shell was very massive, some of the plastral plates 
measuring upwards of 13 mm. in thickness. 
The arrangement of the plates will be best understood from 
the figures. There seems to have been a pygal of peculiar 
form, narrowing towards the margin of the shell (fig. 1, B) : 
it is represented in part by its impression’ only, but the 
sutures can be followed. The lower supra-pygal is a small 
well-defined bone, crescentic in outline, with the concavity 
downwards. The nature of the bone above is doubtful, the 
sutures in this region being obscure and cracks numerous: 
it may be a second sypra-pygal or the posterior pair of 
costals unitingiin the middle line. If this last interpretation 
is correct, the animal possessed at least nine pairs of costals— 
a quite exceptional condition. The marginals were very 
massively constructed : all preserved are much broken at the 
edges. The plastron (fig. 1, A) is chiefly remarkable for the 
presence of two mesoplastrals on the left side, while there is 
only one on the right. This reduplication of the plastral 
element is interesting, because it may indicate a tendency to 
revert to an earlier condition in which the number of paired 
elements in the plastron was greater than inlaterforms, The 
posterior lobe narrows gradually backwards from the bridge, 
and its posterior end is slightly notched. The anterior lobe 
is broadly rounded ; the form of the epiplastrals cannot be 
clearly determined, but it can be seen that their upper border 
was thickened, rounded, and covered with the characteristic 
sculpture. The entoplastron is incomplete, but was probably 
lozenge-shaped. The hyoplastra are incomplete in front. 
The single mesoplastron on the right side is very wide, 
almost as wide as the two occurring on the other side taken 
together. On both sides the mesoplastra widen out towards 
the bridge, this being particularly marked in the anterior 
one on the left side. The form of the hypo- and xiphiplastra 
present no special peculiarities. The grooves marking the 
outline of the horny scutes are well marked on the plastral 
surface, but could not be seen on what remains of the 
carapace. ‘The boundary between the humeral and pectoral 
scutes crosses just behind the posterior angle of the ento- 
plastron, that between the pectorals and abdominals is on the 
mesoplastra. The grooves between the femoral and anal 
scutes slope strongly backwards, and are confined to the 
xiphiplastra. On the bridge there were three or four sub- 
marginal scutes. ‘The presence of the horny scutes on a 
shell in which the sculpture is so strongly developed seems 
remarkable. 
