34 THE NAUTILUS. 
which are apt to be lost sight of in the excessive elaboration of 
comparatively minor details into generic characters. (See 
Stone, Science, LI, pp. 427-429, 1920.) 
The specific nomenclature adopted is that of the ultra-Rafin- 
esque school and results in the changing of about one-fourth of 
the names in current use. But the last word has not yet been 
said in regard to Rafinesque’s species. Indeed more than a 
year ago the author and the present writer undertook to make a 
careful study of the subject in accordance with the requirements 
of the International Code of Nomenclature, which is now about - 
ready for publication and which it is hoped will go far towards 
definitely settling the nomenclature of the North American 
Naiades. : 
Barring the question of specific names there is much to praise 
and but little to criticize in the synonymy adopted. 
It is possible that some of the conclusions reached by the 
author and based, perhaps, too much on local conditions may 
be subject to revision when an equally detailed study of the 
species throughout their entire range can be made. 
The question of possible hybridization between closely allied 
species along the line of contact, when elsewhere the specific 
characters seem to be fixed is one that must necessarily be taken 
into consideration. 
The author lays great stress upon his theory that small streams 
tend to produce a small, flat form which increases in size and 
rotundity as the river grows larger. While this is apparently 
true in many cases, there are exceptions, some of which are 
noted by the author. Amblema elliotti Lea is another notable 
one. The large, typical form from Othcalooga Creek, a small 
stream, is much larger than any Amblema from the Coosa. On 
the other hand, practically all of the species of the Great Lakes 
are dwarfed and much smaller than the same species from the 
comparatively smaller tributaries. It would seem that possibly 
other factors, such as temperature, food supply, chemical con- 
stituents of the water and other ecological conditions and not 
simply the size of the stream should be taken into consideration. 
But all these are comparatively minor matters which do not 
detract from the worth of the monograph as a whole and which 
