ORTMANN: FAMILIES AND GENERA OF NAJADES. 231 
I have found that the German specimens agree in every particular 
with the American form. Certain characters not observed in my 
specimens (marsupium and glochidia) I have gathered from the 
literature (chiefly Harms, 1907 and 1909). 
Margins of mantle free all around from the anterior to the posterior 
end 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 
Fic. 1. Margaritana margariltifera (Linneus). 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 for 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 is found in front and below that of the outer gill, but separated 
from the palpi by a wide gap.® 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 served as: 
original for our figure) the gap is rather short. 
