SYNOPSIS OF the: XAIADES— SIMPSON-, 711 



tUNIO WEBSTERI B.H.Wright. 



" Unlo websteri B. H. Wright, Pr. Ac. N. Sci. Phila., 1888, p. 113, pi. ii, fig. 2 ' ; 

 ^^ Check List, 1888. 



Florida. 



tUNIO DORSATUS Lea. 



"Uniodorsatus'LKA, Pr. Ac. N. Sci. Phila., XII, 1868, p. 160; * Jl. Ac.N. Sci. Phila,, 

 VI, 1868, p. 300, pi. XLV, fig. 112; * Obs., XII, 1869, p. 60, pi. xlv, fig. 112.— 

 *B. H. Wright, Check List, 1888.—*^ Simpson, Pr. U. S. Nat. Mus,, XV, 1892, 

 p. 411, pi. LI, fig. 7; Lii, figs. 1, 2. 



* Margaron ( TJnio) dorsatus Lea, Syn., 1870, p. 37. 



Catawba Eiver, North Carolina ; Florida. 



fUNIO WACCAMAWENSIS Lea.2 



* Unio ivaGcamawensis Lea, Pr. Ac. N. Sci. Phila., VII, 1863, p. 193; * Jl- Acad. 



N. Sci. Phila., VI, 1866, p. 16, pi. v, fig. 14; *Obs., XI, 1867, p. 20, pi- v, fig. 

 14.— ^B. H. Wright, Check List, 1888. 



* Margaron ( Unio) ivaccamaivensis Lea, Syn., 1870, p. 36. 



Waccamaw Lake, iSorth Carolina. 



(Group of Unio pigerrimus.) 



Shell rather solid, elliptic rhomboid, somewhat inflated, with a low, 

 rounded posterior ridge, sometimes a little arcuate below, biangulate 

 behind ; beaks full, their sculpture a few coarse ridges which are curved 

 upward and swollen where they cross the posterior ridge; surface 

 concentrically striate and often sculptured with curved, subradiating 

 or zigzag corrugations which have a tendency to break into nodules; 

 epidermis brownish; hinge rather heavy; pseudocardinals stumpy, 

 granular; laterals club shaped; muscle scars well marked. 



Animal unknown. 



UNIO PIGERRIMUS Crosse and Fischer. 



* Unio pigerrimus Crosse and Fischer, Jl. de Conch. XLI, 1893, p. 293. — 



"* Fischer and Crosse, Miss. Sc;., Pt. 7, II, 1894, p. 582, pi. lxv, figs. 1, la. 



Mexico. 



tUNIO MITCHELLI Simpson. 



""Unio mitchelli Simpson (in Dall.), Pr. U. S. Nat. Mus., XVIII, 1896, p. 5; Pr. U. 

 S. Nat. Mus., XIX, 1896, p. 371, pi. xxxii, figs. 1-3.^ 



Southern Texas to New Leon, Mexico. 



'Mr. Wright has sent to the Museum under the above name two quite different 

 forms, neither of which is like the figure. From an examination of the first one 

 sent, an old, worn shell, and the figure, I believed it to be a form of U. ohesus (see 

 Proc. U. S. Nat. Mus., XV, 1892, p. 428). Specimens sent since by Mr. Wright and 

 said to be typical approach U. hartwrighti, but are more compressed and elongated. 

 These forms are exceedingly j)uzzliug. 



2 An aberrant species. The shell is inflated, thin, and has a strong posterior ridge. 

 It has characters of both the Buckleyi and Crassidens groups. 



^Close to pigeri-imus apparently, and niny be but a variety of it; it is a lighter, 

 longer shell, is less sculptured, and does not have a rose-colored nacre. 



