746 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL.XXIL 



N. Sci. Phila., VI, 1853, p. 216. *KUSTER, Conch. Cab. Unio, 1852, p. 39, pi. 

 vii, fig. 2. *SO\VEKBY, Conch. Icon., XVI, 1868, pi. LXIX, fig. 354. 



* Pleurobema clava A<;ASSIZ, Arch, fiir Naturg., I, 1852, p. 49. 



* Unio clarus REEVE, Conch. Syst., I, 1841, p. 117, pi. LXXXVIII, fig. 3. * HAN- 



LEY, Test. Moll., 1842, p. 187; * Biv. Shells, 1843, p. 187, pi. xx, fig. 52. *CAT- 

 LOW and REEVE, Conch. Nom., 1845, p. 57. MI. and A. ADAMS, Gen. Rec. 

 Moll., II, 1857, p.495. *B. II. WIUCIIT, Check List, 1888. P.KTEL, Conch. 

 Sam., Ill, 1890, p. 148. * CALL, Tr. Acad. Sci. St. Louis, VII, 1895, p. 9. 

 pi. i. 



* Margarita ( Unio} davits LEA, Syn.. 1836, p. 22; 1838, p. 18. 



* Margaron ( Unio) darns LKA, Syn., 1852, p. 26; 1870, p. 40. 



* t Unio patulus LEA,' Tr. Am. Phil. Soc., Ill, 1829, p. 44, pi. xn, fig. 20; * Obs., I, 



1834, p. 55, pi. xn, fig. 20. * CONRAD, Monog., X, 1838, p. 92, pi. L, fig. 2. 

 *HANLEY,Test.Moll., 1842, p. 187; *Biv. Shells, 1843, p. 187, pi. xxn, fig. 

 27. *CATLOW and REEVE, Conch. Nom., 1845, p. 62. *H. and A. ADAMS, 

 Gen. Rec. Moll., II, 1857. p. 495." CHENU, 111. Conch., 1858, pi. xvi, figs. 6, 6a, 

 66. *KrsTEit, Conch. Cab. Unio, 1861, p. 259. pi. LXXXVII, fig. 5. *B. H. 

 WRIGHT, Check List, 1888. *P/ETEL, Conch. Sam., Ill, 1890, p. 162. 



* Margarita ( Unio) patulus LEA, Syn., 1836, p. 22; 1838, p. 18. 



* Marf/aron ( Unio) patuhis LEA, Syn., 1852, p. 26; 1870, p. 40. 



* Unio cuneattis SAY, Am. Conch., VI, 1834. * FERUSSAC, Guer. Mag., 1835, p. 28. 



Ohio, Cumberland, and Tennessee river systems. Reported from 

 Iowa City, Iowa; St. Peter's River, Minnesota, and from Nebraska. 



t PLEUROBEMA MACULATA Conrad. 



* Unio maculatm CONRAD, New F. W. Shells, 1834, p. 30, pi. IV, fig. 4, p. 70. 



* FERUSSAC, Gner. Mag., 1835, p. 29. MOLLER, Syn. Nov. Gen., 1836, p. 202. 



* HANLEY, Test. Moll., 1842, p. 203 ; * Biv. Shells, 1843, p. 203." CATLOW and 

 REEVE, Conch. Nom., 1845, p. 60. * CHENU, Bib. Conch., 1st ser., Ill, 1845. 

 p. 17, pi. in, fig. 7. * CONRAD, Pr. Ac. N. Sci., Phila., VI, 1853, p. 252.* H. 

 and A. ADAMS, Gen. Rec. Moll., II, 1857, p. 495. *KUSTER, Conch. Cab. Unio, 

 1861, p. 216, pi. LXXII, fig. 2.* B.H.WRIGHT, Check List, 1888. * P.ETEL, 

 Conch. Sam., Ill, 1890, p. 158. 



* Margarita (Unio) macidatus LEA, Syn., 1836, p. 34; 1838, p. 23. 



* Margaron (Unio) maciilatus LEA, Syn., 1852, p. 24; 1870, p. 38. 2 



Tennessee River system. 



t PLEUROBEMA HOLSTONENSIS Lea. 3 



*Unio holstonensis LEA, Pr. Am. Phil. Soc., I, 1840, p. 288; *Tr. Am. Phil. Soc., 

 VIII, 1842, p. 212, pi. xv, fig. 27; *0bs., Ill, 1842, p. 50, pi. xv, fig. 27. *HAN- 



'No specimen in the Lea collection exactly agrees with the figure of this species 

 and Lea gives no exact locality for the type; but from a careful study of his shells 

 and the figure and description I am convinced that it is a somewhat compressed form 

 of the very variable dava, which has rather low beaks, that are not placed as far for- 

 ward as usual. There seems to be a complete set of intermediates. 



2 Dr. Lea is inclined to believe (see above citation) that Conrad's Unio maculaliis 

 is the same as his own rarenelianns, and if this were the case Lea's name should have 

 precedence. From an examination of specimens in the Philadelphia Academy of 

 Natural Sciences and Conrad's figure and description, I am forced to differ from Dr. 

 Lea, as I consider the species close to Lamarck's clavus. 



3 The type, a young shell, is certainly the same as Unio Jawii, and there does not seem 

 to be any material difference between it and the types of U. bellitlns and mnndus. 

 The figure is hardly accurate. 



