NAIADES OF MISSOURI sete) 
ANIMAL CHARACTERS. 
NUTRITIVE STRUCTURES:—Branchial opening with papillae on 
inner edge, anal with fine but distinct papillae; supra-anal long 
and large with very short connection of mantle edge; gills sharply 
pointed behind with wide space between the anterior attachment 
to mantle and base of the palpi, inner laminae of the inner gills 
entirely free from visceral mass; palpi rather large, subfalcate; 
color of soft parts variable, but usually orange yellow especially 
the distal end of foot, also mantle edge and adductors, while sterile 
gills are brownish. 
REPRODUCTIVE STRUCTURES:—Marsupia with crowded septa 
dividing the ovisacs parailel to the gill filaments; when charged, 
lumen of ovisacs somewhat cylindrical containing club-shaped 
conglutinates which are carmine red or pinkish to whitish in 
color; glochidia somewhat small, semicircular, spineless, hinge 
line nearly straight, about as long as high (0.150 x 0.155mm). 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—dShell  trigonal-quadrate, rather 
thick, compressed, rather rounded post-dorsad, gently curved 
ventrad; disk somewhat undulated by growth lines; beaks not 
very high or full, sculptured by concentric ridges breaking into 2 
or 3 nodules at base of posterior ridge; this post-umbonal ridge 
usually flattened; epidermis yellowish to dark horn color, raved 
in well preserved and young shells, eradiate in old. 
INTERNAL STRUCTURES:—Cardinals double in both valves; 
laterals long, serrated; scars well impressed; beak cavity narrowly 
deep; nacre mostly white, sometimes tinged with salmon in beak 
and antero-branchial cavities, irridescent. 
Length Width Diameter Locality. 
65 xX 945 x 30mm (St. Francis River, Greensville, Mo.) 
43 x 35 x 25mm (( ” ” ” 9 x” 
Bomex, 4G" Xue oa ram (White River, Hollister, Mo.) 
34 x 27, x 16mm ( ” ” ” ” ) 
This latter measurement is that of a somewhat advanced 
adolescent shell. However, it shows the juvenile characters of 
a flattened post-umbonal ridge, a rounded post-dorsal line and the 
very distinct concentric sculpturing on the beaks much more 
evidently than in the adult. The most striking characters, that 
are absent in the mature shell, are the green rays. 
