NO. 1205. SYNOPSIS OF TRE NAIADES— SUIPSON. 869 



* Margaron {Triquetra) corrugata Lea, Syn., 1852, p. 17; 1870, p. 25. 



* Triquetra corrugata H. and A.Adams, Gen. Rec. Moll., II, 1857, p. 508. 



* ? Triplodon rugosum Spix, Test. Fluv. Bras., 1827, p. 35, pi. xxix, figs. 1,2. 



* Syria rtigosa Deshayes, Enc. M6th., II, 1827, p. 151, pi. ccxlvii, fig. 2. 



* Mya angulata Wood, Ind. Test. Sup., 1828, p. 3, pi. i, fig. 12. 



* Margarita (Unio) angulatus Lea, Syn., 1836, p. 10; 1838, p. 13. 



* Hyria exasperata Sowerby, Conch. Icon., XVII, 1869, pi. ii, fig. 3. — ^P^etel, 



Conch. Sam., Ill, 1890, p. 189. 



Eastern Peru to Guiana ; south througbout Brazil. 



tHYRIA RUGOSISSIMA Sowerby. 



* Hyria rugosissima Sowerby, Conch. Icon., XVII, 1869, pi. in, fig. 5. — * PiETEL, 



Conch. Sam., Ill, 1890, p. 189. 



Amazon River. 



HYRIA LATIALATA Sowerby. 



* Hyria latialata Sowerby, Conch. Icon., XVII, 1869, pi. ii, fig. 4. — *PiETEL, 



Conch. Sam., Ill, 1890, p. 189. 



Guiana. 



tHYRIA TRANSVERSA Hupe. 



* Hyria transversa Hupe, Moll. Nouv., Ill, 1857, p. 79, pi. xv, fig. 1. — * Sowerby, 



Conch. Icon., XVII, 1869, pi. iv, fig. 7.—* P^tel, Conch. Sam., Ill, 1890, p. 

 189. 



Brazil. 



Subgenus TRIQUETRANA Simpson, 1900. 



(Type, Unio stevensi Lea.' ) 



Shell compressed, with a feebly developed posterior wing, thickened 

 in front; each valve with about three somewhat divergent pseudo- 

 cardinals which are sometimes nearly smooth and at others break into 

 denticles; one granular lateral in the right valve and two in the left 

 which are sometimes obliquely and faintly vertically striate; external 

 sculpture much as in Hyria. Animal unknown. 



tHYRIA STEVENSI Lea. 



* Unio stevensi Lea, Pr. Ac. N. Sci. Phila., I, 1871, p. 188; " Jl. Ac. N. Sci. Phila., 



VIII, 1874, p. 22, pi. VII, fig. 19; *Obs., XIII, 1874, p. 26, pi. vii, rig. 19. 



Yuruari River, Guiana. 



Genus PRISODON Schumacher, 1817. 



(Type, Mya syrmatopliora Meuschen in Grouovius.) 



Triquetra Klein, Tent. Method!, Ost, 1753, p. 135. 



Prisodon Schumacher (part), Essai Nouv. Syst., 1817, p. 138. 



Paxyodon Schumacher, Essai Nouv. Syst., 1817, p. 139. 



Shell aviculiform, solid, somewhat inflated, with a well-developed 

 posterior ridge, the area above it being excavated, its outline from the 



1 This shell bears much the same relation to Hyria that Castalina does to Tetra- 

 plodon, its teeth being more unionoid than those of Hyria and the shell more 

 compressed. 



