20 (J CHELTUIDiE. 



7. Podocnemis tracaxa. 



Eniys tracaxa, Spix, Test. Bras. p. G, pi. v. (1824). 



jiiacroct'pbala, Spi.r, I. c. p. v, pi. iv. 



reltocephalus tracaxa, Bum. 4'- Bihr. ii. p. 378, pi. xviii. iig. 2 

 (1835); Grcni, Cat. Tort. p. 44 (1844), and Sh. licpt. i. p. 01 

 (1855) ; Sfrduch, Verth. Schildkr. p. 101 (18G5) ; Grai/, f^uppl- 

 Cat. Sh. Rept. i. p. 84 (1870). 



Carapace rather convex, obtusely keeled posteriorly. Supra- 

 caudal shield sometimes single. Plastron large, front lobe much 

 broader than the hind lobe, -which exceeds the width of the bridge ; 

 intero-ular shield longer than the gulars ; the longest median suture 

 is formed by the femorals ; suture between the humerals about as 

 long as that between the pectorals. Intcrorbital space flat, broader 

 than the diameter of the orbit ; upper jaw strongly hooked ; jugal 

 bone forming a suture with the quadrate ; a very large interparietal 

 shield, widening behind, and widely separating the parietals ; the 

 width of the mandible at the symphysis much exceeds the diameter 

 of the orbit ; alveolar surface of both jaws with a feeble median 

 ridge. Chin with a short dermal appendage. Three very large 

 shields on the outer border of the foot. Dark brown above, 

 yellowish inferiorly. 



Length of shell 43 centim. 



Amazon, Guianas. 



a, b. Ad., stffd. S. America. 



Fam. 9. CHELYDID^. 



Emydida3, imrt., Gray, Atm. Phil. (2) x. 1825. 



ICmydidse, part., Bell, Zool. Journ. iii. 1828. 



Stegauopodes, part., IVagler, Syst. Amph. 1830. 



Cbelydte, part., Gray, Syn. Rept. 1831. 



Elod'ites Pleuroderes, part., Diimcril i^- Bibron, E^p. Gen. ii. 1835. 



Chelydidfe, part.. Gray, Cat. Tort. 1844, and Sh. Ript. i. 1855. 



Chelyoidae, Hydraspididaj, part., Ayassiz, Contr. N. H. U. S. i. 1857. 



Chelyda, part., Strauch, Chelon. Stud. 1862. 



Hydi-aspididfe, Cope, Rroc. Ac. Philad. 1868, p. 282. 



Clielydida3, Hvdraspididfe, Gray, Suppl. Cat. Sh. Rept. i. 1870. 



Chelydidfe, Bouleyiger, Ann. ^- Mag. N. H. (6) i. p. 347, 1888. 



riastral bones nine. Shell covered with epidermal shields. Neck 

 bending under the margin of the carapace, always exposed ; fifth 

 and eighth cervical vertebra) Idconvex. No bony temporal arch, 

 but usually a paricto-squamosal ; palatine bones separated by the 

 vomer ; nasals usually present ; pnefrontals separated from each 

 other ; deutary bones usually distinct. Digits moderately elongate ; 

 claws four or five. 



South America, AustraUa, and New Guinea. 



