746 PROCEEDINGS OF THE NATIONAL MUSEUM. voL.xxn. 



N. Sci. Phila., VI, 1853, p. 246.— *Kuster, Conch. Cab. Unio, 1852, p. 39, pi. 



VII, fig. 2.— *SoWERBY, Conch. Icon., XVI, 1868, pi. LXix, fig. 354. 



* Pleurobenia clava Aga.ssiz, Arch, fiir Naturg., I, 1852, p. 49. 



* Unio clavus 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 Reevk, Conch. Nom., 1845, p. 57. — *H. and A. Adams, Gen. Rec. 

 Moll., II, 1857, p. 495.— *B. H. Wright, Check List, 1888.— *P^tel, Conch. 

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

 pi. I. 



* Margarita ( Unio) clavus Lea, Syn., 1836, p. 22; 1838, p. 18. 

 * Margaron ( Unio) clavus Lea, Syn., 1852, p. 26; 1870, p. 40. 



*t?7mo palulus Lea,i Tr. Am. Phil. Soc, III, 1829, p. 44, pi. xii, fig. 20; * Obs., I, 

 1834, p. 55, pi. XII, fig. 20.— * Conrad, Mouog., X, 1838, p. 92, pi. l^ fig. 2.— 

 *Hanley, Test. Moll., 1842, p. 187; *Biv. Shells, 1843, p. 187, pi. xxii, 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, 

 6&.— *KUSTER, Conch. Cab. Unio, 1861, p. 259, pi. lxxxvii, fig. 5.— *B. H, 

 Wright, Check List, 1888.— *P^tel, Conch. Sam., Ill, 1890, p. 162. 



* Margarita {Unio) patulus Lea, Syn., 1836, p. 22; 1838, p. 18. 



* Mar gar on (Unio) patuliis Lea, Syn., 1852, p. 26; 1870, p. 40. 



"* Unio cuneatus Say, Am. Conch., VI, 1834. — *Ferussac, Guer. Mag., 1835, p. 28. 



Ohio, Oumberlaiid, and Tennessee river systems. Eeported from 

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



tPLEUROBEMA MACULATA Conrad. 



* Unio maculatus Conrad, New F. W. Shells, 1834, p. 30, pi. iv, fig. 4, p. 70.— 



* Ferussac, Guer. 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. Ill, 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.— *PiETEL, 

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



* Margarita (Unio) maculatus Lea, Syn., 1836, p. 34; 1838, p. 23. 



* Margaron (Unio) maculatus Lea, Syn., 1852, p. 24; 1870, p. 38.^ 



Tennessee River system. 



tPLEUROBEMA HOLSTONENSISLea.3 



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



VIII, 1842, p. 212, pi. XV, fig. 27; *Obs., 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 clava, 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 maculatus 

 is the same as his own ravenelianus, 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. 



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

 to be any material difference between it and the types of U. hellulus and mundus. 

 The figure is hardly accurate. 



