318 CLASS XV. 



Neck very long. Shell depressed, covered with smooth skin. 

 Feet with only three internal toes unguiculate. Tail short. 



The absence of horny plates on the flat shield distinguishes this genus 

 not less than the three-nailed swimming feet. All the species live in fresh 

 water and are carnivorous. Sp. Trionyx JEgyptiaeus GEOFFR., Tesludo 

 triunguis FORSK., GMEL., GEOFFR. S-r.-HiL., Ann. du Mus. xiv. PL i, i, 

 Diet, des Sc. nat., Erp&ol. PL 3 ; this species lives in the Nile and eats the 

 young crocodiles with avidity as soon as they have escaped from the egg. 

 See the skeleton described and figured in C. A. MOHRING Diss. inaug. 

 zootom., sistens descriptionem Trionychos ^Egyptiaci osteologicam, Berolini, 

 1824, 4to; Trionyx /eroas SCHWEIGG., Testudoferox PENNANT, LAC. Quadr. 

 ovip. i. PL 7, Trionyx spiniferus, LESUEUR Me"m. du Mus. xv. p. 258, 

 PL 6 ; this species, which attains a very large size, lives in North America, 

 in the rivers Wabash, Tennesee, and Ohio. Most of the species of this 

 not very numerous genus are from the East Indies. 



Chelys DUME"R., WAGL., Matamata MERE. Covering of beak 

 thin, nearly cutaneous. Nose proboscidian. Head depressed, 

 trigonal. Dorsal shell depressed, small, covered with horny scutes; 

 supracaudal (pygal OWEN) marginal scutella two. Anterior feet 

 with five nails, posterior four. Neck fimbriato-carunculate, not 

 retractile, capable of flexion towards the sides of thorax. 



Sp. Chelys fimbriata SCHWEIGG., Testudo finibriata SCHN., GMEL., SCHOTFF 

 Hist. Testud. Tab. 21 (figure re-engraved from that given by BRUGUIERE, 

 Journ. d'Hist. natur. 1792), DAUD. Kept. n. PL 20, fig. i, SPIX Spec. nov. 

 Test, et Ran. Tab. 1 1 ; Cuv. R. Ani., 6d. ill., Rept. PL 7, fig. 2 ; the only 

 known species of this genus which approaches nearer to Emys than to 

 Trionyx; this animal lives in stagnant fresh water in Guyana and Brasil. 



Emys BRONGN. (DuM.). Covering of mandibles horny. An- 

 terior feet mostly with five nails, posterior with four. Dorsal 

 shield sub-gibbous, covered with horny scutes ; supracaudal margi- 

 nal scutella two. 



This genus is the most numerous in species of the entire order of 

 tortoises ; most of them are met with in America. Emys is a Greek name 

 of tortoises that reside in fresh water. PLINIUS, Hist. nat. Lib. 32, 

 cap. 4. 



t Neck capable of flexure to the sides of shield. Pelvis conjoined with 



Hydraspis BELL, FITZ. (Platemys WAGL., DUM. and BIBR., with 

 addition of some other genera of modern writers). 



Sp. Emys Planiceps SCHW., Testudo planiceps SCHN., SCHCEPFF 1. 1. Tab. 27; 

 Emys Maximiliani MIKAN, Hydromedusa Maximiliani WAGL. Syst. 



