N0.12C5. SYNOPSIS OF THE XAIADES— SIMPSON. 513 



imiDOSsible to tell wMcli of two names appeared first, and in sucli cases 

 I have used that which seemed to be best known. 



Many of the species of Lamarck stand on about the same foundation 

 as those of Eafinesque, having only a brief description and no fig- 

 ures. Dr. Lea on at least two occasions went over the tyj)es of most 

 of Lamarck's species and has published his conclusions in the Obser- 

 vations, and I am obliged to abide by his decisions, never having seen 

 the types myself. 



One of the most perplexing problems has been the work done by 

 European conch ologists, and especially by the so-called new school of 

 Trance. Previous to 1870, the date of issuance of Lea's last edition of 

 the synopsis, thousands of names had been applied to the few sj)ecies 

 of Europe. But this work was conservative and reasonable compared 

 with that of the new school since then. I have devoted much time 

 and study to this fauna and its literature. To me it seems that 

 there are not more than eighteen or twenty species of Unionidcie found 

 in Europe, judging by the same standards I have applied to species 

 elsewhere. ]Srearly all the authors seem to be more or less at sea as to 

 certain forms of this area, and the reasons for this are j)robably their 

 want of striking characters and their extreme variability. Unio picto- 

 rum, tumidus, elongatulus, and i^latyrliynchoideus have been often taken 

 for each other. Margaritana margaritifera has repeatedly been mis- 

 taken for the very similar looking M. crassa, and each of these has been 

 hopelessly confused with Unio hatavus. 



I have endeavored to consider names applied before 1870 in my 

 synonymy. I have made no eftbrt to do this with those applied by 

 authors to the forms of Euroi)e since that time, as I do not believe that 

 any new species of TJnio^ Margaritana ., Anodonta, or Leguminaia have 

 been found there in the last thirty years. The genus GoUetopterum ( 1881) 

 is a doubtful one and is very likely only an mutation of the excessively 

 variable Anodonta cygnea. In 1892 Arnould Locard, one of the great 

 lights of the new school, stated that there were 208 species of Unios 

 and 250 Anodoutas in France alone.^ 



Life is too short and valuable to be wasted in any attempt at 

 deciphering such nonsense, and I have not even cumbered the pages 

 of this work with a list of these new si)ecies. Those interested can find 

 them in the works of Westerlund and Kobelt. 



In cases where the new school has worked on the fauna of Africa or 

 Asia, I have done the best I could to straighten out the synonymy. 



I have not attempted to make any analytical key to genera and other 

 groujjs, because I do not believe that it is possible to construct a key 

 that will be of any real service to the student. At least four-fifths of 

 the shells of the ISTaiades have the beaks so eroded that it is imiDossible 

 to form any idea of what their sculpture is like, and the soft parts are 

 inaccessible to the average student and collector. These are both vital 

 characters that must be used in classification. The general arrange- 

 ment of the groups down to genera is shown in the following table : 



1 Aun. Soc. Ag. Hist. Nat. Lyon, 1892, p. 55. 



Proc. X. M. vol. xxii 33 



