CATALOGUE FAMILY UNIONID.E. 



f Unio zeiglerianus, Lea. 



(Trans. Am. Phil. Soc., Vol. VI, PI. X, Fig-. 27.) 

 Cumberland river, Tennessee. See under V. irix. with which it groups. 



* Unio zigzag, Lea. 



(Trans. Am. Phil. Soc., Vol. III., PI. XII, Fi<r. 19.) 



Ohio to Coosa river, Alabama; to Indian Territory and Kansas; to Minnesota 

 and Wisconsin. Synonymous with U. donaciforrnis, which see. Groups 

 with U. elegans, Lea. 



The following species have been erroneously cited, by various authors, as oc- 

 curring within the Mississippi drainage area: 



Unio complanatus, Solander, Unio nasntns, Say, 

 Unio ochraceus, Say, Unio cariosus, Say, 



Unio radiatiix. Lamarck, Unio nharcensis, Lea. 



The first and last of these belong to a group which is not represented at all in 

 western waters. Two others 77. cariosus and U. ochraccus belong in the 

 lutcolus group; possibly, also, will so group U. radiatus. The western ana- 

 logue of 77. iKtxHtiis is the U. subrostrntns. Say, which is mentioned at length 

 above. These species are all, so far as authentic information goes, confined to 

 the Atlantic drainage. The presence of certain western forms in the Erie canal 

 and Mohawk river, in central New York, on the Atlantic slope, and in waters 

 directly connected with the western drainage system presents an explanation of 

 their occurrence that is not paralleled by the possible presence of the eastern 

 forms in western waters. The western species thus far recognized east of the 

 Atlantic divide in the state of New York are the following: 



T'nio rnltiyinosi'X, Lea. Uniu (jiltlioxnx. Barnes, 

 77mo lutcolus, Lamarck, Unio P/TX.S-NS, Lea. 



All four are forms of wide distribution, but in the case of the species erro- 

 neously cited as-occuring west of the Appalachian system and in waters belong- 

 ing to the Mississippi drainage area, all save one U. complanatus are com- 

 paratively limited in their geographic areas. The extent to which these proposi- 

 tions will be modified can be determined only when very full and complete col- 

 lections shall be made in all streams, flowing in either direction, which rise in 

 the Appalachians. 



In the preceding catalogue those forms which are common to both sides of the 

 Mississippi are indicated by an asterisk [*], those found on the east side alone. 

 by a dagger [f], and those known only from the streams to the westward are 

 indicated by a double dagger Ft], The results of this study of geographic dis- 

 tribution maybe seen in the following recapitulation: 



CATALOGUE 48. 



