The American Midland Naturalist 



PUBLISHED BI-MONTHLY BY THE UNIVERSITY 

 OF NOTRE DAME, NOTRE DAME, INDIANA 



VOL. VI. JULY-SEPTEMBER, 1920. NOS. 10, 11 



Variation in Nacreous Color of Certain Species of Naiades Inhabiting 

 the Upper Ohio Drainage and their Corresponding Ones in Lake Erie. 



BY N. M. GRIER, PH. D. 



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I. — Introductory and Statement of Problem. 



Perhaps the greatest amount of the systematic study of color in 

 any animal group has been given to the birds, where the demand for 

 a more accurate color terminology in describing the hues of pluma- 

 ages eventually resulted in the Ridgeway Color Standards and 

 Color Nomenclature, (14), — a scientific achievement apparently 

 but little appreciated by others than ornithologists. Other types 

 of animals, such as the Insects and even the Gastropods have been 

 by no means neglected at least from the standpoint of variation in 

 color pattern, but the fresh water mussels, (Naiades), so far as the 

 writer is aware have not been the subject of any but more incidental 

 observation. 



One who has formed some acquaintance with any scientific 

 work dealing with color nomenclature, must become impressed 

 with the apparent glittering generalities in the specific description 

 of shells so far as epidermal and nacreous color are concerned, 

 but lest it be thought there exist no justification for this seeming 

 slovliness on the part of the student of the Naiades, it need only 

 be pointed out that in the case of birds at least, they are probably 

 less numerous in collection, species for species, than mussel shells. 

 Moreover, they possess a distinct advantage in that their plumage 

 colors are usually arranged in a definite color pattern, or so asso- 

 ciated with sexual or other characters that the ornithologist may 

 well use them more accurately for descriptive purposes, than the 

 conchologist can with the data he even may more laboriously 

 collect. There has thus been a proportionate development of the 



