186 
Records of the Geological Survey of India, 
[voL. X.U. 
On a marginal bone of an undesceibed tortoise, from the Upper Siwaliks, 
NEAR Nila, in the Potwae, Punjab, hy W. Theobald, Geological Survey of 
India, 
The bone which forms the subject of the present remarks, and of which a 
figure of the natural size is given, is remarkable for exhibiting a structural adapt¬ 
ation which exists in no living species, and, so far as I am aware, has not yet been 
described in any fossil. It will be necessary, therefore, to refer it to a new genus 
which I propose to associate with the name of the illustrious fellow-worker of 
Falconer, Colonel Cautley, and characterize as follows:— 
Cautleta. 
Genus Emydinorum, novum, in quo sternum, et thorax, et ossa marginalia, 
sutura tripartite cartilagine& junguntur, sectionem morsum hirudinis simul- 
antem monstrante. 
The above character suffices to demonstrate the distinctness of the species 
under consideration from any previously described, and the specific designation 
is derived from the most prominent character of the animal as yet known, and 
in the annular arrangement of the marginal hones. 
C. ANNULIGEK, n. S. 
The marginal hone, whereon I base the above genus and species (and which, 
except a slight fi-acture at one corner, is perfect), is trapezoidal in shape and 
cuneiform in section. It presents an upper and under surface, respectively slightly 
concave and convex, which were shown to have been external surfaces by the 
clearly marked fm-row which traverses them, and indicates the junction of the 
superficial or dermal scutes (fig. 1, a h, fig. 2, cd). The hone is hounded laterally 
by a jagged sutural surface, whereby a complete and rigid bony union was 
effected between it and the adjoining marginals, which must have constituted 
an encircling bony ring of an extremely rigid character, from the great horizontal 
breadth of the hones in question. The peculiar and characteristic feature, how¬ 
ever, of the bone lies in its internal margin (fig. 3, efg) which displays a smooth 
surface, indicating a cartilaginous union only, with the bones of the sternum and 
thorax. This inner marginal surface is obscurely divided into two areas of 
unequal breadth, of which the lower is broader and opposed to the sternal plate, 
whilst the upper and narrower surface receives the thrust of the bones of the 
thorax. The thorax and sternum were no doubt united by a cartilaginous suture, 
as a cartilaginous junction with the marginal is opposed to the idea of a rigid bony 
union between the bones in immediate contact with them, since a rigidly anchylosed 
bony ring united only by cartilage to bones themselves joined by a bony suture, 
could lend no additional strength, though it undoubtedly would do so supposing 
it to cover and defend a cartilaginous union of the sternal and thoracal bones. 
The length of the external margin is 5'0 inches, w'hich indicates approximately 
an animal close on 10 feet in circumference. The condition of the suture shows 
that the individual was not of full age, and 12 or 14 feet may probably be assumed 
