THE CLASSIFICATION AND GEOGRAPHICAL DISTRIBU- 

 TION OF THE PEARLY FRESHWATER MUSSELS. 



By Charles T. Simpson, 



Aid, Department of Molliisks. 



The naiades, or pearly fresh- water mussels, have a universal distribu- 

 tion throughout the ponds, lakes, and streams of the world, not only on 

 the continents, but on most of the larger and some of the smaller islands. 

 Some of the genera have probably extended back with but little change 

 to the beginning of Mesozoic or possibly well into Paleozoic time; hence 

 their study is an extremely interesting one, which may help us in 

 obtaining a knowledge of the distribution of other life, and the muta- 

 tions of land and sea in time past. 



I. CLASSIFICATION OF THE NAIADES. 



In 1800^ and 1812^ Lamarck established the family of Nayades, which 

 he afterwards changed to Naiades,^ and in which he i>laced two genera, 

 (nio and Anodonta. In 1819 he added the genera Hijria and Iridina, 

 but i)laced Castalia wrongly in the family Trigoniacea, an error which 

 was rectified by Ferussac in 1822, by Latrielle in 1825, by Blainville in 

 the same year, and by Menke in 1828. In 1820 Rafinesque^ created the 

 family Pediferia for Unio, Anodonta, and several related genera, includ- 

 ing Cyclas. 



Blainville in 1825^ refused to accept the classification of Lamarck, 

 and made a family Submytilacea, with the genera Anodonta, Unio, and 

 Cardita, thus returning to the errors of Poll, who in 1795^ gave the name 

 Limncea to animals inhabiting the shells belonging to the genera Unio, 

 A nodonta, and Cardita. 



The name Unionidte was created in 1828 by Fleming,^ and adopted 

 afterwards by Gray," Swainson,^ and other modern authors.'" 



1 Philosophie Zoologique, p. 328, 1805. 



^Extrait du Cours de Zool., p. 106, 1812. 



3 Phil. Zoologique, I, p. 318, 1830, 



^ Ann. Geuer. Sciences Physiques, p. 290, 1820. 



5 Man. de Malacol. et ConchylioL, p. 537, 1825. 



^'Testacea Utriusque Sicilia', II, p. 253, 1795. 



' Hist. British Animals, p. 408, 1828. 



«In Turton, A Manual of the Laud and Fresh-water Shells, p. 288, 1840. 



* Treatise on Malacology, p. 259, 1810. 



' ' The names of Lamarck, Ratinesque and Blainville can not be considered, since it 



18 a rule in nomenclature that a family or 8nl)faniily name must be founded on one 



of its principal genera. Hence Unionidw must take precedence. 



Proceedings of the United States Nation.il Muscuiii, Vol. XVIII — Xo. 1008. 



2ii5 



