THE NAUTILUS. 131 



Some 63 genera are recognized in the Unionidce, over two-thirds of 

 them being formed from the old genus Unio of authors, while 

 Margaritana has also been dismenbered. Anodonta is retained in 

 nearly its old limits, except that the South American forms have 

 been transferred to the genus Glabaris of the Mutelidce, a change 

 made by Dr. von Ihering some years ago. While a large portion of 

 the genera are based upon the peculiarities of the ovisacs or other 

 internal organs, Mr. Simpson finds that " when these are once dis- 

 covered and understood, it will be found on careful examination that 

 there are minor shell characters that correspond with those of the 

 marsupia" so that a vast number of species unknown anatomicallv 

 can be correctly grouped generically by the shells alone, although in 

 some cases the record is not thus easily to be read. This is about 

 the way the case stands in the Helicidce; and in fact tallies with con- 

 clusions reached by workers on widely diverse groups of mollusks. 

 The people who decry "mere shell characters" as valueless, are 

 those who know little about them; but the fact remains that without 

 knowledge of the internal anatomy, the real significance and compara- 

 tive value of the shell characters could never have been discovered. 

 Practical conchologists should give Mr. Simpson's system the test of 

 rearranging their species by it. We hazard little in saying that 

 once this is done, the naturalness of his generic groups will win gen- 

 eral acceptance for the new classification. In many cases one cannot 

 but he struck by the happy grouping of species which never before 

 seemed to fit in anywhere. 



Regarding the synonymy, Mr. Simpson seems to have exercised 

 fair and temperate judgment. He is no species-splitter, but on the 

 other hand, he has steered clear of an equally dangerous reef, which 

 has wrecked several promising investigators. In other words, he has 

 never allowed the reaction toward extreme " lumping " of species, 

 which followed the era of Lea, to warp his judgment. As it is, the 

 list of synonyms under some species, such as Unio cotnplanatus, 

 tiwnteyi, obesits, etc., is appalling. The treatment of the Lumpsilis 

 parvus group is particularly commendable. 



In the geographic relationships of the genera, a close affinity 

 between the groups of southeastern Asia and tropical Africa is stated 

 to obtain. This accords with the distribution of Amputlariida, 

 Viviparidce, and many land shells such as ZmiitidcE and Strepfaxidce. 

 The faunal relation between the mollusks of eastern Asia and 



