THE NAIADES OF MISSOURI ‘ 249 
the lack of papillae or other specialized structures (as related to 
the processes of reproduction) in the region of the branchial open- 
ings. Since the species of this group are mostly lacustrine we find 
them, of course, mostly distributed in the chain of lakes along the 
Missouri River or in the ponds and small sluggish streams of the 
interior of the state north of the Missouri River. Compared to 
the other sub-families, we do not find so many variations in this 
Sub-Family due to the more constant ecological conditions to which 
the Anodontine species are remarkably constant—especially as 
to reproductive structures, in which respect they differ from those 
of the Lampsilinae; however, the Anodontine species are like the 
Unionine in the possession of large palpi, whereas those of the 
Lampsiline species are small. In all probability the larger palpi 
are for reproductive as well as nutritive purposes. It is interesting 
to note the recapitulation of the evolution of the whole race of _ 
Nazades in some of the individual members of this Sub-Family 
in that the coarse sculpturing, noted on the disk of juvenile shells, 
is carried back up to the umbones in mature shells—a progression 
from the sculptured disk of the more primitive to the smooth 
disk of the more modern forms of the adult. 
Genus, Symphynota Lea. 
1829—Symphynota Lea, Tr. Am. Phil. Soc., III, p. 424. 
(Type, Symphynota compressa lea) 
ANIMAL STRUCTURES :—Branchial opening with short papillae; 
anal smooth, or finely crenulated; supra-anal larger or smaller 
than anal, separated by more or less long mantle connection; 
gills bowed ventrad, septa and water-tubes well developed, 
inner lamina of inner gills free from visceral mass; marsupium 
occupying outer gills, pad-like and with secondary water tubes, 
when charged; glochidia large, spadiform, spined, hinge line 
undulate; palpi sickle-like united for one-half of their length 
anterio-dorsad; color of soft parts usually yellowish. 
SHELL CHARACTERS:—Shell elliptical to oval, compressed, 
smooth except for costae sometimes on posterior dorsal ridge; 
beak sculpture double looped, or sinuate-concentric; cardinals 
always present; laterals imperfect, or even absent; nacre white 
or bluish. 
MISCELLANEOUS REMARKS:—The shell characters of Symphy- 
nota would relate it more closely to the more primitive group than 
