218 CHELYDID.®. 
Neural plates present, four in number; nuchal shield present, 
marginal. Plastron large, with very strong axillary, and mode- 
rately strong inguinal buttresses, the latter anchylosed to the fifth 
costal plate. A very slender parieto-squamosal arch ; parietals not 
expanded superiorly ; jaws moderately strong, without alveolar ridges. 
Chin with a pair of dermal appendages. Digits entirely webbed. 
South America, 
Shell of Rhinemys nasuta. 
1. Rhinemys nasuta. 
Emys nasuta, Schweigg. Prod. p. 29 (1814). 
barbatula, Gravenh. Delic. Mus. Zool. Vratisl. p. 15, pl. v. 
figs. 8 & 4 (1829). 
Hydraspis barbatula, Gray, Syn. Rept. p. 43 (1831). 
Platemys schweiggeri, Dum. § Bubr. ii. p. 485 (1835). 
Hydraspis nasuta, Gray, Cat. Tort. p. 40 (1844). 
spixii (non D. §& B.), Gray, Proc. Zool. Soc. 1852, p. 134, 
raniceps, Gray, Cat. Sh. Rept. i. p. 55, pl. xxiii., and Proce, Zool. 
Soc. 1864, p. 180, and Suppl. Cat. Sh. Rept. i. p. 74 (1870), and 
Ann. § Mag. N. H. (4) xi. p. 74, fig. (1873). 
