a OUTS ONS ONE IN PLAN? C HHL ONT A: 
By N. ANNANDALE, D.Sc., F.A.S.B., Superintendent, 
Indian Museum. 
The majority of the specimens mentioned in these notes have 
been sent me by Dr J. R. Henderson of the Madras Museum, 
who has been at great pains, in this and other respects, to assist 
us in the Indian Museum with specimens from the Madras Presi- 
dency. 
Family TRIONYCHIDAE. 
Trionyx leithii, Gray. 
1873. Tvrionyx leithit, Gray, Proc. Zool. Soc. London, p. 49, fi 
(skull). 
1873. Tvrionyx gangeticus, id., 1btd., pl. viii. 
1889. Tvrionyx leith, Boulenger, Cat. Chel. Brit. Mus., p. 249. 
1912. Tvrionyx leitiiz, Annandale, Rec. Ind. Mus., VII, p. 159, 
fig. 2 (plastron of young). 
Boulenger regards this species as intermediate between 7. 
gangeticus, which it somewhat resembles in colouration, and 7. 
hurum, with which the shape of its skull is to some extent in 
agreement; but the structure of the skull is nearer that of T. 
formosus. ‘The only differences that I can detect are that the 
snout is a little less declivous and slightly longer, the horizontal 
groove on the palate broader, the post-cranial spine less dilated 
and the proximal articular part of the lower jaw more slender in 
T. letthit than in the Burmese species. The former has much the 
same relationship to the latter as T. nigricans has to T. phayret, 
and the existence in T. Jetthiz of two neural bones between the 
first pair of costals is a modification probably of slight importance 
though it serves to separate all the Indian forms from their Bur- 
mese allies. The branchial skeleton of T. leithii also resembles 
that of 7. formosus, in particular in that two additional ossifica- 
tions are present at the tip of the hypobranchial bone. In the 
adult animal the hypoplastra approach one another in the middle 
line of the plastron, though they do not actually meet, and the 
internal projections practically disappear. 
The natural colouration and the external appearance of the 
disk do net appear to have been observed in the adult living ani- 
mal. ‘The following notes are based on two individuals which 
Dr. Henderson has been kind enough’ to send to Calcutta for 
examination. . 
