STATION IN FRESH-WATER MUSSELS. 285 



Unio flavidiis Lea, '72 (Clinch R., Anderson Co., Tenn. ; Holston 

 R. ; N. Ala.). — Synonym to PI. tiiscumbiensis, according to Simp- 

 son, 1. c. 



Dia. (Lea) : 52 per cent. 

 I have measured the following material. 



Loc. No. Max. Min. Av. 



Tennessee River. 



Chota Shoals 4 66 51 61 appr. 



Holston River. 



Turley Mill i 46 46 46 cuu. 



Noeton 10 59 45 51 appr. {cun.) 



Holston Station 2 47 45 46 cun. 



Austin Mill 3 54 45 48 cun. (appr.) 



North Fork Holston River. 



Rotherwood 10 45 39 41 cun. 



Hilton 8 43 36 40 cun. 



Mendota 8 46 38 41 cun. 



The general rule, from the Tennessee up the Holston, is seen. 

 Irregularities and more sudden changes (from the Tennessee to the 

 Holston, and from the latter to the North Fork) may be accounted 

 for, on the one hand, by scarcity of material, or, on the other, by the 

 sudden transition from a larger river to a smaller one. 



I leave out some material collected in tributaries of the Ten- 

 nessee and Holston, because it is fragmentary : but I should say 

 that it does not conflict with the rule. From the Clinch River, I 

 am able to offer the following table. 



Loc. No. Max. Min. Av. 

 Clinch River. 



Solway I 55 55 55 appr. 



Clinton 7 57 47 51 appr. (cun.) 



Offutt I 52 52 52 appr. 



Black Fox Ford 3 45 40 43 cun. 



Clinch River Station 6 45 40 43 cun. 



Oakman 7 49 39 44 cun. 



Horton Ford i 39 39 39 cun. 



Speers Ferry 9 42 ^6 40 cun. 



Clinchport 6 44 38 41 cun. 



The sudden change of obesity between Ofifutt and Black Fox 

 Ford undoubtedly is due to the fact that a long stretch of the river 



