98 THE NAIADES OF MISSOURI 



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 diflfer from those 

 of the Lampsilinae; however, the Anodontine species are like the 

 Unionine in the possession of large palpi, whereas those of the 

 Lawt;f'577zw£' 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 

 Naiades 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 



