IIYRIA I213 



ridge well developed, often subangular above and semi-double 

 below, where it ends in a feeble biangulation ; dorsal outline 

 arched, extending into a decided wing in front and behind; 

 anterior end narrowed, cut away below, posterior end usually 

 obliquely truncate, often incurved ; epidemiis greenish-brown ; 

 pseudocardinals compressed, much split up; laterals long and 

 straight in young shells, short and curved in old ones, all the 

 teeth more or less vertically striate; nacre usually lurid, some- 

 times silvery, thicker in front in old shells. 



Length 107, height 63, diam. 27 mm. 



Length 94, height 60, diam. 34 mm. 



Eastern Peru to Guiana; south throughout Brazil. 

 Hyria corrugata Lamarck, An. sans Vert., VL 1819, p. 82. — 



SowERBY, Rec. and Foss. Shells, 1823, No. XVL fig. d; 



G^nch. Man., 1839, fig. 144. — Ree;vE, Conch. Syst., I, 1841, 



p. 120, pi. xc, fig. 2. — KusTER, Conch. Cab. Unio, 1856, p. 



140, pi. xhi, fig. I.— Chenu, Man., 1859, H, p. 149, fig. 733. 



— Reeve, Elem. Conch., H, i860, pi. xxxi, fig. 179. — Sower- 



BY, Conch. Icon., XVH, 1869, pi. i, fig. i. — Simpson, Syn., 



1900, p. 868. 

 f Unio corrugata Bi.ainville, Man., 1825, p. 539, pi. exvii, 



fig. I. 

 Margaron (Triquetra) corrugata Lea, Syn., 1852, p. 17; 1870, 



p. 25. 

 Triquetra corrugata H. and A. Adams, Gen. Rec. Moll., H, 



1857, p. 508. 

 ? Triplodon rugosum Spix, Test. Fluv. Bras., 1827, p. 35, pi. 



XXIX, figs. I, 2. 



Hyria rugosa Deshayes, Enc. Meth., H, 1827, p. 151, pi. 



CCXEVII, 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. 11, 



fig-3- 



This seems to be an abundant species and subject to great 

 variation, and for that reason it has received many names. 



