286 ANNALS OF THE CARNEGIE MUSEUM. 
Genus ANoponTA Lamarck. (1799.) 
Simpson, 19008, p. 620. 
Shell elliptical, or elongated; thin; flat, or inflated, with smooth 
disk. Beak-sculpture distinct, but not very heavy, of the double- 
looped type, the loops separated by a sinuation, or a reéntering angle. 
Hinge-teeth completely absent. 
Only the outer gills are marsupial. When charged, the edge dis- 
tends, and secondary water-tubes are present. Ovisacs not sub- 
divided. No placentze are developed. Inner lamina of inner gills 
free from abdominal sac. Mantle-connection between anal and 
supra-anal generally very long, longer than either opening. 
Type A. cygnea (Linnezus). 
In the reduction of the hinge-teeth, in the long mantle-connection 
between anal and supra-anal, and the whole structure of the shell, 
this genus represents a very extreme specialization of the anodontine 
type. In the free inner lamina of the inner gill it is rather primi- 
tive. 
A large number of species are recognized by Simpson (19000), but 
in Europe the species-making in this group has gone beyond all the 
bounds of reason. A healthy reaction is, however, setting in, with 
regard to this genus as well as the European genus Unio (see Kobelt, 
1908, p. 91; Thiele, 1909, p. 33; Israél, 1909, p. 26; Haas, 1910c). 
As will be shown below, the European genus Pseudanodonta, which 
has been split off, is also unsatisfactorily supported. It remains to 
be seen, whether the species from western North America and Asia 
have the same structure of the soft parts. Certain Chinese forms 
differ in the beak-sculpture. 
Anodonta cygnea (Linnzus). 
See also Ortmann, I9IIc, p. 22. 
A large number of specimens of both sexes, including gravid females, 
from various places in Germany and Hungary have been sent to me 
by W. Israél. 
I agree with Isra®l (1909) in regarding all Anodontas of central 
Europe (except complanata), as one species. The form cellensis is 
surely only the senile form of ponds, and anatina is the form of small 
creeks. The name of this species should be cygnea and not piscinalis. 
