X SYNOPSIS OF 



In the following tables there will be found in the Family, 1069 recent species as 

 admitted, 224 unknown to me or doubtful, and 183 fossil ; in all 1476 ; and the 

 synonymy according to my views is enormous, being 891. 



Of the subgenus Triquetra {Klein), 1 there are 4 species and 25 synonyms. 



Of the subgenus Pfisodon (Schumacher),' 1 3 species and 13 synonyms. 



Of the subgenus Unio (lietzius), there are 833 species in a recent state and 501 

 synonyms. In addition there are 141 which I have not been able to admit as certain; 

 of fossil species 169. 



Of the subgenus Margaritana (Schumacher), there are 29 admitted species, and 

 6 which are unknown to me. There are 66 synonyms. 



Of the subgenus Plagiodon (Lea), there is 1 species. 



Of the subgenus Monocondylcea (D'Orbigny), there are 26 species, and 4 un- 

 known to me. There are 27 synonyms. 



Of the subgenus Dipsas (.Leach), I know of but 2 species, both of which are 

 recent. There are 20 synonyms. 



Of the subgenus Anodonta (Cuvier), there are 148 admitted species, and 68 

 which are unknown to me. Of fossil species there are 14. Of synonyms there are 

 189. 3 



Of the subgenus Columba (Lea), there are 2 species, and 13 synonyms. 



Of the subgenus Byssanodonta (D : Orbigny), 1 species. 



Of the subgenus Iridina (Lamarck), there are 4 species, and 3 unknown to me. 4 

 There are 6 synonyms. 



Of the subgenus Spatha (Lea), there are 9 species, all recent, and 2 unknown 

 to me. There are 22 synonyms. 



Of the subgenus Mycetopus (D' Orbigny), there are 8 species, and 8 synonyms. 



Most of the distinguished authors who have written on the subject of the division 

 of this Family, have acknowledged the extreme difficulty they have encountered in 

 separating it into natural groups. This difficulty is not peculiar to the Unionidoe. 

 In most of the Families where a great number of species has been observed, we find 



1 Tentamen Methodi, 1753. 



2 Nouveau Sysleme, 1817. 



3 To Anodonta cygnea alone I make 100 synonyms, and I believe that many in my doubtful list will 

 be found to be mere synonyms to this prolific species, which has been a mine to ambitious species makers. 



4 Mr. Gray, in his List of Genera, Pro. Zool. Soc, 1847, gives priority to Scopoli, Intro, ad Hist. 

 Nat., 1777, under the name of Mutela. Scopoli adopts Adanson's name of Mutel, and adds the a to it. 



