THE NAIADES OF MISSOURI 389 
developed; beaks low, sculptured by the early bars of fine con- 
centric arrangement and later one of double-looped type—some- 
times rather nodulous at base of post ridge; sexually dimorphic, 
the female shell being wider posteriorly by the expansion of the 
post-ventrad edge of shell. 
MISCELLANEOUS REMARKS:—With the exception of unique 
glochidium and more developed hinge this genus stands with 
Lasmonos. Proptera is represented in this state by the four species: 
alata, which is found mostly in Central Mo., purpurata which 
only occurs in South Mo., laevissima which is mostly restricted 
to North Mo., and capax which is entirely confined to the Miss- 
issippi River. The last named species has not been definitely 
settled within any genus before on account of a lack of an exact 
determination concerning the morphology of its animal. The 
extreme inflation of the capax shell,,as compared to the compressed- 
type of the other members of this genus, would seem to shut it 
out, but glochidial and marsupial characters (besides its similar 
beak sculpture) are by far more reliable affinities. All the members 
of this most sharply defined genus are long period breeders. 
Proptera alata (Say). 
(‘Razor Back,’’ ‘‘Rudder Back,’’ ‘Hatchet Back,”’ 
‘Pant 'Cakey*) 
1 ANT LIE) RET COL, 
1816— Unio alatus Say, Nich, Encyc., II, pl. IV, fig. 2. 
1898—Lampsilis alatus Baker, Moll. Chicago, Pt. I, p. 97, pl. XVIII. 
1912b—Proptera alata (Say) Ortmann, An. Car. Mus., VIII, p. 333. 
ANIMAL CHARACTERS. 
NUTRITIVE STRUCTURES :—Branchialand anal openings inclined 
to tubular structure, branchial upcurved, small with numerous 
papillae; anal smooth thick edges; supra-anal large thick and 
close mantle connection to anal; inner laminae of inner gills 
entirely connected to visceral mass; palpi about as wide as long, 
connected about one-half of their length antero-dorsad; color 
of soft part tan-flesh color with dark mantle edges and orange 
colored cerebral ganglion. 
REPRODUCTIVE STRUCTURES :—Marsupia large, occupying pos- 
terior half of outer gills, consisting of large ovisacs sulcated ventrad 
mantle edge antero-ventrad to branchial opening lamelar with 
