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 Algyp- 
tiacus (Trionyx Afgyptiacus), 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. 4igyptiacus ; 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. 4igyptiacus. 
«‘ With respect to the Gymnopus Euphraticus (Trionyx Euphrati- 
cus), originally described by Olivier (Voyage en Perse, tom. 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- 
