712 PEOCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



tUNIO IHERINGI B. H. Wright. 



* Unio ilieringi B. H. Wright, Naut., XII, 1898, p. 93. — * Simpson, Pr. Ac. N, Sci. 

 Phila., 1900, p. 79, pi. iv, fig. 5. 



Southern Texas. 



t UNIO SPHENORHYNCHUS Fischer and Crosse. 



*Unio sphenorhynchus Fischer and Crosse, Miss. Sci., Pt. 7, II, 1894, p. 617, pi. 

 Lxvr, figs. 2, 2a. 



Mexico. 



(Group of Unio Uehmanni.) 



Shell rather solid, inflated, ovate rhomboid or trapezoidal, with a 

 well-developed posterior ridge, pointed at or near the base behind, but 

 not biangulate, nearly straight or slightly incurved below; beaks full, 

 sculpture not seen; surface smooth or concentrically striate; epidermis 

 dark, scarcely rayed; hinge rather strong; pseudocardinals heavy, 

 compressed; muscle scars distinct; nacre livid to whitish. 



Animal unknown.^ 



tUNIO LIEBMANNI Philippi. 



* Unio liebmanni Philippi, Zeits. f iir Mai. , IV, 1847, p. 96 ; * Abbild. und Besch., Ill, 



1849, p. 109, pi. VI, fig. 1.—* KusTER, Conch. Cab. Unio, 1862, p. 281, pi. xciv, 

 fig. 7. — *PiETEL, Conch. Sam., Ill, 1890, p. 157. — * Fischer and Crosse, Miss. 

 Sci., Pt. 7, II, 1894, p. 616. 



* Margaron ( Unio liebmanni) Lea, Syn., 1870, p. 48. 



* Unio liebmanni B. H. Wright, Check List, 1888. 



Mexico. 



tUNIO OPACATUS Crosse and Fischer. 



* Unio opacatiis Crosse and Fischer, Jl. de Conch., XLI, 1893, p. 295. — *' Fischer 



and Crosse, Miss. Sci., Pt. 7, II, 1894, p. 592, pi. lxvi, figs. 1, la. 



Mexico. 



(Group of Unio huckleyi.) 



Shell oval, obovate, subtrapezoidal, or elliptical, with a more or less 

 developed posterior ridge, often biangulate behind, compressed or 

 inflated, thin or somewhat solid; beaks generally full, sculptured with 

 several rather strong concentric ridges, which are either nearly paral- 

 lel with the growth lines or slightly doubly looped ; posterior slope 

 often faintly wrinkled; epidermis usually smooth and shining in the 

 younger shells, often rough when old, becoming darker with age, rayed 

 when young. Hinge teeth solid or compressed; nacre mostly brilliant, 



'This group is exceedingly close to that of U. hucldeyi, according to the shell char- 

 acters, and some specimens of U. liebmanni are so near others of U. buckleyi as to 

 deceive even experts. 



