738 PROCEEDINGS OF THE NATIONAL MUSEUM. TOL.XXII. 



|UNIO POPEII Lea. 



* rio popeii LEA, Pr. Ac.N. Sci. Phila., IX, 1857, p. 102; *J1. Ac.N. Sci. Phila., 



l\, 1858, p. 372, pi. LXVI, fig. 197; * Obs., VIII, 1860, p. 54, pi. LXVI, fig. 197. 



* Unio popei SOWERBY, Conch. Icon., XVI, 1868, pi. LXXXI, fig. 430. * B. JI. 



WRIGHT, Check List, 1888. * P.ETEL, Conch. Sam., Ill, 1890, p. 164. 



* FISCHER and CROSSE, Miss. Sci., Pt. 7, II, 1894, p. 605. 



* Margaron ( Unio) popeii LEA, Syn., 1870, p. 57. 



South Texas ; northeast Mexico. 



fUNIO POEYANUS Lea. 



* Unio poeyanus LEA, Pr. Ac. N. Sci. Phila., IX, 1857, p. 85; * Obs., VI, 1857, p. 3-">, 



pi. xxxn, fig. 30; * Jl. Ac. N. Sci. Phila., Ill, 1858, p. 315, pi. xxxn, fig. 30. 



* SOWERBY, Conch. Icon., XVI, 1868, pi. xc, fig. 486. *B. H. WRIGHT, 

 Check List, 1888.* P^TEL, Conch. Sam., Ill, 1890, p. 164.* FISCHER and 

 CROSSE, Miss. Sci., Pt. 7, II, 1894, p. 606. 



* Margaron ( Unio) poeyanus LEA, Syn., 1870, p. 57. 



Eio de las Balsas, near Coyucan, Mexico. 



UNIO VER^-PACIS Tristram. 



* Unio verat-pacis TRISTRAM, Proc. Zool. Soc. Lond., 1863, Pt. 3, p. 414. l *B. H. 



WRIGHT, Check List, 1888. * P^TEL, Conch. Sam., Ill, 1890, p. 171. 



* FISCHER and CROSSE, Miss. Sci., Pt. 7, II, 1894, p. 620. 



Guatemala, Department of Vera Paz. 



Section CANTHYRIA Swainson, 1840. 



Shell inflated, suboval, spinose, with a high, rather sharp posterior 

 ridge, above which it is somewhat truncated, the posterior slope being 

 sometimes slightly wrinkled ; beaks rather compressed, the sculpture 

 not seen; epidermis smooth and shining, variegated with angular 

 blotches; hinge sharply curved at the center; pseudocardinals rather 

 compressed ; laterals short, remote, the hinge plate narrowed ; beak cavi- 

 ties rather deep. Animal with the roarsupiuin occupying the whole of the 

 outer gills, forming a smooth pad; branchiae very large, round below, 

 inner the larger, free nearly their whole length from the abdominal 

 sac; palpi large; mantle double on its edge, sometimes with a few 

 papillae in front of the branchial opening; branchial opening small; 

 superanal opening colored inside. 2 



t Unio spinosus LEA, Desc. of New Sp. Unio, 1836, colored figs. ; * Tr. Am. Phil. Soc., 

 VI, 1838, p. 57, pi. xvi, fig. 50; *Obs., II, 1838, p. 57, pi. xvi, fig. 50. * JAY, 

 Cat., 1839, p. 113, pi. \, figs. 1, 2. * TROSCHEL, Arch, fur Naturg., V, 1839, Pt. 

 2, p. 236. *HAjnasY, Test. Moll., 1842, p. 182; *Biv. Shells, 1843, p. 182, pi. 



'Only a Latin description was given by Tristram, and the species is not identifi- 

 able. It is probably close to U. popeii, and may possibly be that. 



2 Notwithstanding the remarkable character of well-developed spines on the only 

 species of this group, U. spinosus, the animal even when gravid does not present any 

 striking peculiarities, and is certainly a Unio. I have seen one or two specimens of 

 the spinosus with only one spine on one valve and none on the other, and one in the 

 Lea collection without spines. 



