Ortmann: Families vnd Genera of Najades. 



23] 



I have found thai the German specimens agree in every particular 

 with the American form. Certain characters no1 observed in my 

 specimens (marsupium and glochidia) I have gathered from the 

 literature (chiefly II. inns. 1907 and 1909). 



Margins of mantle free all around from the anterior to the posterior 

 (•ml and with no tendency to unite anywhere. Branchial opening 

 indistinctly separated from the anal, a horizontal ridge running from 

 the posterior insertion of the outer lamina of the outer gill to the margin 

 of the mantle, but the margins of the mantle are not held together by 

 the diaphragm. Anal opening not closed above, and no supra-anal 



^br 



Fig. 1. Margaritana margaritifera (Linnaeus). Specimen from the Perl-Bach, 

 Postfelden, Bavarian Forest, Germany. (Carn. Mus., No. 61, 4,987.) 



formed. Branchial opening ill-defined anteriorly, on the inner edge 

 with strong papillae, which disappear anteriorly, and then the inner 

 edge of the mantle is smooth. Inner edge of anal opening almost 

 smooth. 



Palpi large, subfalciform, drawn out and pointed behind, their 

 posterior margins united tor about one-half to three-fourths of their 

 length. 



Gills long and broad, the inner the wider, chiefly so anteriorly. 

 Outer gill becoming gradually narrower in front, its anterior end at 

 the highest point of the line of attachment of the mantle, high above 

 the palpi. Inner gill narrowing more suddenly anteriorly. Its anterior 

 end i> found in front and lulow that of the outer gill, but separated 

 from the palpi by a wide gap. 6 Edge of inner gills with a longitudinal 

 furrow, which is absent in the outer gills (this character is present in all 

 Najades examined, and will not be mentioned again). 



6 This character is variable, and sometimes (as in the specimen which serve I as 

 original tor our figure) the gap is rather short. 



