IQI2. ] N. ANNANDALE: The Indian Mud-Turtles. 16g 
Genus CHITRA, Gray (1844). 
Boulenger, Fauna, p. 16: Siebenrock, p. 608. 
This genus, of which only one species is known, is easily 
recognized by the elongate appearance of the skull, the eyes being 
situated close to the snout, and the complex form and unusually 
complete ossification of the branchial skeleton. The plastron! and 
carapace do not differ materially from those of Tvionyx. The 
photographs reproduced on plate vi show clearly the general struc- 
ture and proportions of the branchial skeleton, although its 
position relative to the skull is perhaps a little distorted. The 
basal part consists of four pairs of bones either sutured in the 
middle line or narrowly separated. Those of the most anterior 
pair (fig. 2, 1) are in close contact with one another for the greater 
part of their length as well as being firmly sutured to the next 
pair. They are roughly triangular in shape and probably represent 
the basihyal element, although they are not produced into horns 
at the sides. Behind them follow three other pairs of bones which 
may be taken to be the basibranchial; those of the first pair are 
smaller than those of the two posterior pairs and remain separated 
in the middle line even in old individuals. Those of the next pair 
are transverse in shape and form a median suture ; they support 
the greater cornua, which are articulated to their sides. These 
bones are comparatively stout and long and are not expanded 
dorso-ventrally ; they bear very large and well-developed muscular 
impressions near the proximal end of their external margin. The 
posterior processes are of great size and considerably expanded in 
the lateral plane, their ossification being unusually complete. Each 
consists of three broad bones fitted together by serrated sutures. 
The first of these is much the longest of the three and probably 
represents the hypobranchial and ceratobranchial fused together. 
In this case the second bone would be the epibranchial and the 
third the ptervgobranchial. The former is a short piate of bone, 
the latter, although no broader at its outer margin, is bluntly 
produced towards the ventral margin in such a way that it is more 
than twice as broad within as it is without. The whole process 
curves inwards and upwards towards its fellow. In the large 
specimen mentioned below the length of the bony hyoid apparatus 
is nearly as great as the skull; the basal part measures 9 cm., 
each horn 11 cm., and each posterior process 13 cm. in length. 
Io. Chitra indica (Gray) (pl. vi, figs. I, 2). 
DISTRIBUTION.—The Ganges and Irrawaddi river-systems, as 
far as the base of the Himalayas in the former. The species is not 
uncommon in the Gangetic delta and large individuals can often 
be bought in the Calcutta market, in which, however, they are 
less abundant than T. hurum and T. gangeticus. 
1 Siebenrock, S.B.K. Akad. Wiss. Wien, CXI (1), p. 833, fig. 12, 1902. 
