NO. 1205. SYNOPSIS OF THE NAIADES SIMPSON. 863 



Genus TETRAPLODON Spix, 1827. 



Castalia LAMARCK, An. sans Vert., VI, 1819, p. 66. 

 Tttraplodon SPIX, Test. Fluv. Bras., 1827, p. 32. 

 Prisodon LEA, Synopsis, 1852, p. 18. 



Shell triangular, solid, inflated, with a high, sharp, posterior ridge, 

 behind which it is decidedly truncated; beaks very full and high, 

 sculpture strictly radial, or with one or two pairs of the central bars 

 coalescing below, the whole extending more or less over the disk as 

 strong ridges; epidermis thick, dark, dull colored; hinge line arched; 

 there is a very strong, compressed pseudocardinal in the left valve, and 

 there are two in the right, all in front of the beaks; behind them are 

 several denticles; one lateral in the right valve and two in the left; all 

 the teeth strongly vertically ridged; beak cavities deep, not com- 

 pressed; anterior muscle scars small, fleep; nacre whitish. 



Animal having the labial palpi wider than long; margins of mantle 

 iuferiorly open, but united posteriorly to form two siphons, branchial 

 and anal; branchial opening surrounded with papillae; anal opening 

 smooth; outer branchiae united to the mantle to their posterior ends; 

 inner united to the abdominal sac; foot tongue-shaped, thick, produced 

 anteriorly. (Troschel.) 



(Type, Tetraplodon pectinatum Spix.) 1 

 (Group of Tetraptodon ambiguus characters, as in the genus.) 



t TETRAPLODON AMBIGUUS (Lamarck) Sowerby. - 



*? Prisodon truncatus SCHUMACKER, Ess. Nouv. Syst., 1817, p. 139. 



*? Castalia ambig 11 a LAMAIICK, An. sans Vert., VI, 1819, p. 67; GUERIN, Icon. Regue. 

 An., 1829, pi. xxviii. * WYATT, Man. Conch., 1838, p. 65, pi. xi, fig. 5. 

 *CHENU, Man., 1859, II, p. 149, fig. 735. * SOWERBY, Conch. Icon., XVII, 

 1869, pi. i, fig. 1. 



* Unio ambigua DESIIAYES, Tr. Elem. Conch., 1839, p. 18, pi. xxix, figs. 7-9. 



* Unio ambiguus SOWERBY, Eec. and Fos. Shells, XVI, 1823, fig. d. * REEVE, 



Conch. Syst., 1841, p. 117, pi. LXXVII, fig. 2. *CATLOW and REEVE, Conch. 

 Nom., 1845, p 55.* DESHAYES, Tr. Elem., II, 1853, p. 219, pi. xxix, figs. 7-9. 

 * KUSTER, Conch. Cab. Unio, 1856, p. 165, pi. XLVIII, fig. 1. 



* Tetraplodon pect'matum SPIX, Test. Fluv. Bras. ,1827, p. 32, pi. xxv, figs. 3-4. 



*t Caxtaliainflata D'ORBIGNY, Guer. Mag., 1835, p. 43.* HANLEY, Test. Moll., 1842. 



p. 173; * Biv. Shells, 1843, p. 173, pi. xxiv, fig. 12. *D'ORBIGNY, Voy.Am. 



Mer., 1843, p. 598, pi. LXXII, figs. 4-10. 

 *t CastaUa turgidallui'K, Moll. Nouv., Ill, 1857, p. 76, pi. xiv, fig. 1. * SOWERBY, 



Conch. Icon., XVII, 1869, pi. in, fig. 11. 



1 The name CastaUa applied by Lamarck to this genus in 1819 can not stand, as it 

 was used in Vormes in 1817. I have every reason to suppose that the young in this 

 and all the South American genera of Unionidce are carried iu the inner gills. 



2 Schumacher gave only a brief description of his Prisodon truncatus, and referred 

 to no figure, and the same can be said of Lamarck regarding his Castalia ambigua, 

 both of which are supposed by authors to lie the above species. But either of these 

 descriptions apply equally well to several species, therefore they can not be con- 

 sidered authentic. 



