594 ORTMANN— NAYADES OF 



are, as Simpson states, much like " Pleiirobcrna appressus," that is 

 to say, Lexingtonia dolahclloides conradi (Van.). I have examined 

 these in Washington. Also specimens in the Walker collection, la- 

 beled abacus, from Flint River, Gurley, Aladison Co., Ala., are this. 



Margaritana ouadrata Lea (1861) — Eastern Tennessee. 

 Symphynota qiiadrata Simpson, '14, p. 487. 



The type is lost. This species never has been recognized. I 

 have the suspicion, from description and figure, that it is identical 

 with Alasmidonta minor (Lea), 1845. 



LIST OF LOCALITIES, AND OF THE NAYAD-FORMS 

 FOUND AT THEM. 



The following list is submitted for two reasons : first, to give an 

 idea of the richness of the material upon which this paper is founded ; 

 second, to facilitate, for subsequent collectors, the search for cer- 

 tain forms. There will be a time, not far distant, when the fauna 

 of many of the localities will have deteriorated or disappeared in 

 consequence of stream pollution, and thus it is important to know all 

 the localities where a given form has been found. The exact location 

 of all the collecting stations is given on the accompanying map, so 

 that also a change of local geographic nomenclature will not inter- 

 fere. (See page 523.) 



The localities have heen arranged according to river systems, be- 

 ginning in the northwest (Powell), and proceeding downstream and 

 eastward. The smaller streams not belonging to the headwaters, 

 have been placed together at the end of each system. The Ten- 

 nessee proper stands at the end of the list. 



Forms found intergrading at one locality are connected by 

 braces. In several instances of well-known and easily recognized 

 species, I have not taken home specimens at certain localities, but 

 only seen them (mostly dead shells). These are marked " sccn!^ 

 The record of this fact always was made in the field with actual 

 specimens before me, and is absolutely reliable. 



