672 i'i;i)ci-:i-:i)iNGS OF THE NATIONAL MUSEUM. YOI..XXU. 



Tennessee and Cumberland river systems. 

 Untigured species. 

 Margaritana etowahensis COXRAD, Pr. Ac. Nat. Sci. Phila., IV, 1849, p. 154.' 



Etowah liiver, Georgia. 



Subgenus BULLELLA Simpson, 1900. 

 (Type, Maryaritana arcitla Lea.) 



Shell thin, greatly inflated, somewhat triangular, with a high, sharp 

 posterior ridge; beaks very full, having exceedingly strong, concen- 

 tric sculpture, extending well on to the disk; pseudocardinals reflexed, 

 compressed. 



Animal with the gills large, nearly semicircular below, inner the 

 larger, united the whole length to the abdominal sac; mantle border 

 with square spots. 2 



tALASMIDONTA ARCULA Lea. 



* Margarita (Margaritana) arcitla LEA, Syu., 1836, p. 43; 1838, p. 27. 



* Margaritana arcula LEA, Tr. Am. Phil. Soc.,VI, 1838, p. 71 . pi. xxn, fig. 69 ; * Obs., 



II, 1838, p. 71, pi. xxn, fig. 69.* TROSCHEL, Arch. fur. Nat., V, 1893, Pt. 2, p. 

 238.* CHENU, Man., 1859, II, p. 144, fig. 712.* B. H. WRIGHT, Check List, 

 1888. * P.ETEL, Conch. Sam., Ill, 1890, p. 172 



* Unio arcula HANLEY, Test. Moll., 1842, p. 210; Biv. Shells, 1843, p. 210, pi. xxn, 



fig. 49. * CATLOW aud REEVE, Conch. Nom., 1845, p. 56. * SOWERBY, Conch. 

 Icon., XVI, 1866, pi. XLVIII, fig. 259. 



* Margaron (Margaritana) arcula LEA, Syn., 1852, p. 42; 1870, p. 67. 



* Alasmodonta arcula CONRAD, Pr. Ac. N. Sci. Phila., VI, 1853, p. 262. 



* Baphia arcula H. and A. ADAMS, Gen. Rec. Moll , II, 1857, p. 500. 



* Margaritana (Alaftmodonta) arcula CLESSIN, Conch. Cab. AUG., 1876, p. 272, pi. 



LXXXIII, figs. 7,8. 

 Altainaha Itiver, Georgia. 



tALASMIDONTA TRIANGULATA Lea. 



* Margaritana Iriangulala LEA, Pr. Ac. N. Sci. Phila., II, 1858, p. 138; * Jl. Ac. N. 



Sci. Phila., IV, 1859, p. 228, pi. xxxn, fig. Ill; *Obs., VII, 1859, p. 46, pi. 



xxxii, fig. 111.* KCSTER, Conch. Cab. Unio, 1862, p. 303, pi. c, fig. 6.* B. H. 



WRIGHT, Check List, 1888. 

 *Unio triangulataSovfERK'Y, Conch. Icon., XVI, 1868, pi. LXXX, tig. 414. 



* Margaron, (Margaritana) triangtdata LEA, Syn., 1870, p. 68. 

 *Margaritana triangulatus P^ETEL, Conch., Sam., Ill, 1890, p. 174. 



South Carolina and Georgia. 



The following species are unknown to me: 



*Alasmodon (Decurambis) atropurpureum RAFINESQUE, Cont. Monog., 1831, p. 5. 

 *Alasmodon (Decurambis) scriptum RAFINKSQUE, Cont. Monog., 1831, p. 5. 



1 Allied to ravenelianus LEA, according to Conrad. 



2 In the only gravid specimen seen the outer gills were curiously wrinkled and 

 folded longitudinally, though the inner gills were plain. If this were a normal 

 character it would entitle the species to generic rank, but I can not feel certain that 

 it is. A. triangulata seems to stand between this and the ordinary Alasmidontas. 



