NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 863 



Genus TETRAPLODON Spix, 1827. 



Castalia Lamakck, Ad. sans Vert., VI, 1819, p. 66. 

 Teiraplodon Spix, Test. Fluv. Bras., 1827, p. 32. 

 Prisodon Lea, Synopsis, 1852, p. 18. 



Sliell triangular, solid, iutiated, with a liigb, 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, deep; nacre whitish. 



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

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

 and anal; branchial opening surrounded with papillae; anal oi^ening 

 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.)' 



(Group of Tefraptodon amhiguus characters, as iu the genus.) 



t TETRAPLODON AMBIGUUS (Lamarck) Sowerby. - 



*'^ Prisodon truncatus Schumacker, Ess. Nouv. Syst., 1817, p. 139. 



* ? Castalia amhigna Lamarck, Au. sans Vert., VI, 1819, p. 67 ; Guerin, Icon. Regne. 



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, pLi, fig. 1. 



* Unio amhigua Deshayes, Tr. Elem. CJonch., 1839, p. 18, pi. xxix, figs. 7-9. 



* TJnio amhiguus Sowerby, Eec. and Fos. Shells, XVI, 1823, fig. d. — ''Eeeve, 



Conch. Syst., 1841, p. 117, pi. l'xxvii, fig. 2. — * Catlow and Eeeve, 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 pectinatmn Spix, Test. Fluv. Bras. ,1827, p. 32, pi. xxv, figs. 3-4. 



*t Castalia inflata 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 Castalia turgidalluvE, Moll. Nouv., Ill, 1857, p. 76, pi. xiv, fig. 1. — * Sowerby, 

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



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

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

 and all the South American genera of Unionidw are carried in 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 anibigua, 

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

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

 sidered authentic. 



