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TRIONYX MVTICJJS.—Lesueur. 



Plate 11. 

 Characters. Shell subround, ecarinate, entire, and without spines or tubercles. 



Synontmes. Trionyx muticus, Lesueur, Mem. du Mus. d'Hist. Nat, torn. xv. p. 263, 

 tab. vii. 

 Trionyx muticus, Leconte, Ann. Lye. Nat. Hist. N. Y., vol. iii. p. 96. 

 Trionyx muticus, Gray, Synops. Rept., p. 46. 

 Trionyx muticus, Harl., Med. and Pliys. Res., p. 159. 

 Gymnopus muticus, Dum. et Bib., Hist. Nat. des Rept, torn. ii. p. 482. 



Description. The shell is subround, entire, slightly arched, smooth or without 

 spines on its anterior border, and without tubercles on the superior surface either 

 of its anterior or posterior cartilaginous margin. 



The sternum is similar in form to that of the Trionyx ferox. 



The head is oval, less elevated at the forehead than in the last species, with 

 the snout equally prolonged, and the nares at its anterior extremity. The nostrils 

 are, however, very diflerently disposed, being large, closely approximated, and of 

 an elliptical form, the larger portion below, and the long axes of the ellipses 

 converging from below upwards and forwards. The eyes are near; the pupil 

 black, and the iris of pale lemon colour, with a dusky bar. The jaws are similar 

 to those of the Trionyx ferox, but more pointed and narrow; the lips are moro 

 developed, and mouth larger in proportion. 



The anterior extremities are short, thick, flattened, with several scales at the 

 Vol. IV.— 3 



