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 



