Richmond Group in Ohio and Indiana. — Nickles. 217 
the genus Strophomena as now understood, — at least King 
and Davidson so understood them, and they really established 
the genus, — though they do not suit Strophomena planumbona 
as its deltidium is much narrower than that represented in de 
Blainville's figures, a character which would not likely be mis- 
represented in a drawing, nor does the general outline of S. 
planumbona agree with the figures. At the same time it must 
be remembered that de Blainville expressly credits the genus 
to Rafinesque. But de Blainville's rugosa (which was almost 
certainly not Rafinesque's rugosa) is not recognizable from 
figures or description. S. A. Miller, in the paper already cited, 
takes the ground that as alter nata has typified, by a sort of un- 
written consensus of opinion, Strophomena in American pal- 
eontological usage for fifty years, it should be regarded as the 
type, and so Hall and Clarke's genus Rahnesquina, based on 
this species, is superfluous. With this conclusion the writer 
cannot agree. 
The purpose of the fundamental law of priority in the bio- 
logical sciences is to secure fixity and stability, to prevent the 
confusion engendered by having a diversity of names for the 
same object, or one name for different objects. We shall never 
. know what Rafinesque's rugosa was. We do not know what de 
Blainville's rugosa is. It is not impossible that the specimen 
figured by de Blainville, the type, may still be found in some 
one of the collections in Paris, if the original label has been 
preserved with it. The figures given, in the writer's opinion, 
are too inaccurate to permit the recognition of the specimen 
from them, unless they represent a species which no one has yet 
suspected of identifying as ,S. rugosa. 
Under the circumstances and with present light, it seems to 
the writer that the wisest solution of the difficulties and the one 
that observes the real intent, if not the exact letter of the law of 
priority, is to recognize, with Rafinesque for its author, the 
genus Strophomena as understood by King, Davidson, Hall 
and Clarke, Winchell and Schuchert, with the Strophomena 
planumbona (Hall) as its type, and drop the name rugosa al- 
together. It is with this interpretation that the name Stroph- 
omena planumbona ( Hall) has been used in this paper. 
