878 rnocEEi>iM,s or THE NATIONAL J/TNATU. VOL.XXH. 



t DIPLODON DIVARICATUS Lea. 1 



* Unio diraricalu* LEA, Tr. Am. Phil. Soc., V, 1834, p. 64, pi. ix, fig. 24; * Obs., I, 



1834, p. 176, pi. ix, fig. 24.* HANLEY, Test. Moll., 1842, p. 197; * Biv. Shells, 

 1843, p. 197, pi. xxin, fig. 36. *CATLOW and REEVE, Conch. Norn., 1845, p. 

 58. *H. and A. ADAMS, Gen. Rec. Moll., II, 1857, p. 494. - v JICKKLI, Faun. 

 Moll. N. O. Af., 1874, p. 280. *P,ETEL, Conch. Hani., Ill, 1890, p. 151. 

 "Margarita ( Unio) divaricatus LEA, Syn., 1836, p. 29 ; 1838, p. 21. 



* Maryaron ( Unio) divaricatm LEA, Syn., 1852, p. 31 ; 1870, p. 49. 



South America. 



f DIPLODON BINNEYI Lea.* 



*Unio linneyi LEA, Tr. Am. Phil. Soc., IV, 1845, p. 16f ; *Tr. Am. Phil. Soc.,X, 

 1848, p. 77, pi. vi, fig. 18; * Obs., IV, 1848, p.51,pl.vi, fig. 18. * CONRAD, Pr. 

 Ac. N. Sci. Phila., VI, 1853, p. 245.* H. and A. ADAMS, Gen. Rec. Moll., II, 1857. 

 p. 493. *B. H.WRIGHT, Check List, 1888. * P/ETEL, Conch. Sam., Ill, 1890, 

 p. 146. 



* Margaron ( Unio) Unneyi LEA, Syn., 1852, p. 29 ; 1870, p. 46. 



South America. 



(Group of Diplodon granosus.} 



Shell elliptical to subtrapezoidal, somewhat compressed, rather thin, 

 beaks low, the sculpture irregularly radial, the ridges narrow and sharp, 

 separated by wide, trough-like spaces, the outer in particular often 

 becoming somewhat nodulous or corrugated, the inner approaching and 

 united below; surface sometimes slightly concentrically ridged and 

 granose; teeth delicate, compressed; nacre bluish. 3 



Animal unknown. 



t DIPLODON GRANOSUS Bruguiere. 



* Unio f/ranosa BRUGUIERB, Jl. tie Hist. Nat., I, 1792, p. 107, pi. vi, figs. 3, 4. 



* LAMARCK, An. sans Vert., VI, 1819, p. 79.* DESHAYES, Enc. Meth., II, 1827, 

 p. 151, pi. CCXLIX, fig. 2. 



* Unio granosus HANLEY, Test. Moll., 1842, p. 182; *Biv. Shells, 1843, p. 182, pi. 



xxni, fig. 21. * CATLOW and REEVE, Conch. Norn., 1845, p. 59. * H. anil A. 

 ADAMS, Gen. Rec. Moll., II, 1857, p. 496.* DROUET, Moll. Guyane, 1859, p. 86. 



1 Credited by Lea to Egypt, but no doubt a South American species, as it has 

 regular radial beak sculpture and appears to belong with this group. 



2 Dr. Lea believes that this shell came from Alabama, but it certainly did not. It 

 is undoubtedly a South American form. The type, the only shell I have seen is 

 dead and in bad condition; but the beaks have radial sculpture, and I think it he- 

 longs here. 



r> No wide distinction exists between this and the preceding group, and there are 

 species which might be assigned about as easily to one as the other. In general the 

 forms of this division are more delicate, thinner, and more compressed than those of 

 the Delodontus group. There are fc\v clear characters in any of the species. I'hilippi 

 and others have, it seems to mo, unduly multiplied names for these forms, and the 

 lack of suitable material and their extreme simplicity and similarity make it impos- 

 sible for me to always determine which are valid. The synonymy is in bad shape, 

 but I have done the best I could at straightening it out. 



