60 Zoological Society. 



large freshwater Tortoise, presented by Lieut. Mawe, R.N., who 

 found it in South America in the year 1833. 



It is marked by Mr. Fraser " Emys Mawii, Bibron, original of M. 

 B.'s description, No. 6899," but I can find no such species described 

 in M. Bibron's work, nor is it an Emys as defined by that author. , 



It differs from all the known Emydse in being covered with very 

 thin membranaceous scales, and in having a broad sternum with a 

 series of four large distinctly defined plates placed over the sterno- 

 costal suture. The gular plates are very small, and there are no 

 axillary or inguinal plates. 



My genus Platystemon has the same kind of sterno-costal plates, 

 but quite a differently formed shell. The head is very large and the 

 tail elongate. 



Dermatemys, n. g. 



Ch. gen. — Testa ovalis, gibba, acarinata, in lateribus rotundata, mar- 

 gine posteriore expanso, paulo reflexo, scutellis membranaceis 

 tenuissimis defenso. Scutella marginales posteriores lata?. Ster- 

 num planum anterius rotundatum posterius emarginatum. Squama 

 gulares parvse, triangulares, testae superiori per longum symphysin 

 affixse. Sutura sterno-costalis squamis magnis quatuor defensa, 

 postremis duabus maximis squamis, minima anteriore. Scutellce 

 axillares et inguinales nulla?. Testa vix ad aperturam contracta. 



Head ? Toes webbed ? Claws ? 



Shell oblong, convex, not keeled ; sides rounded, hinder edge ex- 

 panded, slightly reflexed, covered with very thin membranaceous 

 shields. The hinder marginal shields broad. Sternum flat, rounded 

 in front, notched behind : the gular plates small, triangular, united 

 to the upper shell b)r a long symphysis ; the sterno-costal suture 

 covered with four large distinctly defined plates ; the anterior smaller, 

 the two hinder largest. The axillary and inguinal plates none. The 

 cavity of the shell is scarcely contracted at the opening. 



Hab. South America. 



Dermatemys Mawii, n. s. — Vertebral plates: 1st broad, seven- 

 sided ; 2nd, 3rd and 4th longer than broad. Colour pale brown ; the 

 upper surface covered with small, close, irregular depressions of a 

 darker brown colour ; the shields pale, nearly transparent, very brittle 

 when dry; the under surface uniform pale yellowish white, with 

 slightly sunken grooves. 



Length of upper shell 1 7 inches j width 1 1 inches ; length of ster- 

 num 12| inches. 



Remarks. — The specimen appears to be not quite full-grown. It 

 has much of the external appearance of Phrynops Geoffroyii, and the 

 general thinness of the scales of Chelydidce ; but there is no appear- 

 ance of any scar on the inner surface of the sternum for the attach- 

 ment of the pelvis ; and though the gular scale is worn and nearly 

 obliterated, yet it is sufficiently distinct to show that it has no inter- 

 gular plate. 



