518 Zoological Society. 



" Total length, from the tip of the muzzle to the end of the tail, 

 two feet ; width about one foot ; head and neck, measuring to the 

 anterior edge of the carapace, seven and three quarters inches : cara- 

 pace slightly convex and oval, slightly truncated posteriorly ; com- 

 posed of nine costal plates, the ribs being eight in number ; a double 

 mesial furrow runs along the back, leaving a slightly convex elevation 

 between them : between the first, and most anterior, of these plates 

 and the second, are two depressions, each about half an inch in di- 

 ameter, placed near the mesial line, and separated by a space less 

 than a quarter of an inch in extent. The whole upper surface of the 

 carapace, excepting at the margin, irregularly reticulate. The de- 

 pressions between the costal plates are well marked. The length of 

 the carapace is nine inches, and the breadth seven and three quarters 

 inches ; on the sides of the body the coriaceous membrane extends 

 about two inches beyond the lateral margins of the carapace, 

 the ribs themselves extending about one inch and a half beyond the 

 carapace. Towards the hinder part of the body the membrane gra- 

 dually increases in width, and posteriorly over the tail it had at- 

 tained a width of nearly six inches : here the free portion of the 

 membrane is about two and a half inches in width. The head is in 

 the form of an elongated triangle ; the snout is considerably pro- 

 duced and attenuated : the width of the head at the base is two inches 

 and a quarter ; the total length of the skull is three inches five lines ; 

 the space from the eye to the upper lip, beneath the nostrils, is eleven 

 lines ; the space between the orbits is five lines ; on the vertex, above 

 and between the orbits, the skull is smooth and convex. In both 

 the fore and hind feet the first or front claw is the largest. The tail 

 is rather short and thick ; its length is about four inches and a half. 

 " When alive this animal was of an uniform mud colour, slightly 

 tinted with olive- green. 



"In many respects this animal agrees with the Gymnopus JEgyp- 

 tiacus {Trionyx Mgyptiacus), as described by M. Bibron, but neither 

 the head nor the margin of the carapace is spotted with yellowish 

 white, as in that species ; besides, the two nearly confluent de- 

 pressions on the anterior part of the carapace are not alluded to 

 in the account of G. JEgyptiacus ; they are, however, very conspicu- 

 ous in the animal in question. There are, it may be added, no pel- 

 lucid scales, placed in a transverse direction, on the under surface 

 of each elbow, nor are there any depressed convex tubercles, either 

 anteriorly or posteriorly, on the cartilaginous expansion of the cara- 

 pace, as are often, though not invariably, found in the G. JEgyptiams. 

 " With respect to the Gymnopus Euphraticus {Trionyx Euphrati- 

 cus), originally described by Olivier (Voyage en Perse, torn. iii. p. 453, 

 tabl. 41.), the carapace is described as being broader behind than be- 

 fore, which, if reference be extended only to the osseous disc, is not 

 the case in the present animal. As in that species, however, the 

 circumference of the carapace is smooth, and the skin is folded at 

 the elbow-joint above, but does not simulate scales. The circum- 

 stance of a mesial depression, or rather double channel, with a con- 

 vex line between, down the vertebral column, is not noticed as cha- 



