424 (March 1, 
Cope. ] 
A single nearly bi-lateral bone of this series appear to be either nuchal 
or caudal, but as it has no sutural connection with any other it is not 
easy to determine which is. Its marginal length is much less than its 
transverse extent, which consists chiefly of a flat lamina. The marginal 
part is a little thickened and bi-laterally concave below, and correspond- 
ingly convex above. The margin is thin and acute. A few grooves rad- 
iate at a distance from the middle towards the margin. The lack of con- 
cave excavation of the margin would incline the balance in favor of the 
view that this bone is the caudal. 
A very long gently curved bone is probably the marginal extending on 
one side of the nuchal. It is nearly twice as long as the others, and has 
anextensive and thin superior lamina. Its (?) anterior part is in one plane, 
but the margin soon thickens and displays a rather wide infero-external 
face. It appears to have had an inferior lamina on its posterior half, 
which made an angle with the face just described. An oval cavity in- 
cluded, looks as though designed for the apex of the rib. 
The variation in the lengths of these marginal bones is noteworthy. I 
give measurements, premising that a few lines may be added to the ex-. 
tremities of some for lost digitations: 
M. 
Length of long anterior (11 im.)........... 5... eee es 0.28 
Wadth = CC y (SOMC 1OSb) ei ee 5. ee. 6s 135 
Length of lateral with inferior face........ Pie sei Real ila) 
Width = COUCH ORO eee, ee fe ald 
Length ‘‘ with narrower inferior face....... » 1 08 
Width (Ganka MOOI cote amet tie 6s ces o 115 
Length of one with interior lamina..... Se an eee en ek 
Width =~ (SOME TOS) ee eed ores ote. 050 
Length of a thinner, no inferior plate.....-........ a eve 
Length still thinner, “ vy Ler BONG Oe 
Width of ~ (DIOKGW) iccuns sive ties e ase ee ee ao . 
Ajenoth thinnest, .. 6... 6s fe ee tee eu ah, LOR 
Width (Oe (early, COMplOte):. sues eg vce. ALOU 
(?) Caudal lerigth,............. a ana! es et 
re WAQUMG coe Serene oe ester CO Stat) Patae 150 
The shortness of the marginal with large interior lamina is noticeable. 
as also the same peculiarity in the caudal. As compared with marine 
turtles, difference is to be observed in every particular. Such are the 
lack of sutural union, the laminar character ; the great extent of the 
superior and distinctness of lower lamina. There is no trace of epi- 
dermal sutures visible anywhere. 
A single symmetrical plate appears to have belonged to the middle line 
of the back or nape. It was sub-triangular in outline, all the margins 
yery thin, and with an obtuse keel extending on the middle line, on the 
posterior (or anterior) two-thirds to the apex. This ridge disappears in 
(?) front by a gradual expansion. The surface is marked by lines of minute 
