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1869. | DR. J. E. GRAY ON THE TORTOISES. 21 
3. TRIONYX. 
The odd bone of the dorsal disk covered with a pitted coat in the 
young animals. The genus may be divided into sections thus :— 
* Head short, broad (about as long as broad at the ear-bone), rounded 
in front. The alveolar surface of the lower jaw concave, with 
sharp raised inner and outer margins, and an indistinct short 
central ridge on the inner side of the front. The central pala- 
tine groove in front of the internal nostrils very wide, as wide 
in front as behind. 
1. TRIONYX GANGETICUS. 
** The head rather elongate (rather longer than the breadth at the 
ears), rather tapering in front. The alveolar surface of the 
lower jaw as wide in front as on the sides, slightly concave, 
with a central longitudinal ridge across the front, and with a 
slight concavity on each side. The central anterior palatine 
groove shallow, narrow in front and wide behind. 
2. Trionyx JeupI. (Fig. 19, p. 218.) 
Hab. Java? From the Museum of Prof. Lidth de Jeude. 
This species is described from a fine adult skull received from the 
Utrecht Museum, which, no doubt, was obtained from some of the 
Dutch colonies. It is most distinct from the Indian species. I have 
named it after the Professor who formed the Museum. The front 
longitudinal ridge is very distinct in the jawbone, almost more so 
than in the horny beak of the jaw. The front of the jaw of the 7’. 
gangeticus is simply concave, without any indication of a ridge, but 
only a slight prominence on the inner part of the inner edge; and 
the alveolar surface on the sides of the lower jaw is flat and with.a 
deep oblong concavity on each side. 
In the British Museum there is the head of an adult animal in 
spirit that was purchased of Mr. Theobald, who obtained it in Pegu. 
It has the narrow central anterior palatine groove, and the cylindri- 
cal ridge across the front of the lower beak, of this section of the 
genus; but the ridge is only slightly raised and very different from 
that in the skull from Utrecht. 
3. TRIONYX FoRMOSUS. (Plate XV. fig. 1.) 
This species is described from a young specimen in spirit, pro- 
cured by Mr. Theobald from Pegu. 
The back shield olive, with four very large black-eyed spots, the 
central spot circular, black, with a narrow white margin, and a dark 
brown ring close to it, which is surrounded by a larger pale brown 
ring, separated from the inner one by a broad olive space. The 
outer ring forms part of a regular series of netted dark lines, which 
are symmetrical on the two sides of the keel, forming a large open 
space in the middle of the back, and a smaller one near the margin 
and on the hinder part of the disk. The underside of the margin 
of the disk sooty grey, paler in part, with a white edge on the margin 
