. 
THE NAIADES OF MISSOURI 397 
sisting of twenty ovisacs, well marked, occupying posterior half 
of outer gills, somewhat distended transversely and also at distal 
ends below the origina] line of sterile marsupium; border of mantle 
antero-ventred to branchial opening greatly specialized into a 
double row of red papillae terminating in a knobbed caruncle, 
which, under (x87) lens, is cellular—each cell being hexagonal in 
shape; conglutinates white, discharged whole, club-shaped; 
glochidia medium in size, sub-elliptical, hinge line straight, spineless, 
measures 0.175 % 0.100. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell very small, rather thick, 
elliptical, rounded before, disk without sculpture; beaks low with 
six coarse regular, parallel bars evenly curved up at foot of post- 
ridge region; epidermis brownish to reddish or olivaceous, cloth- 
like female shells broader posterior ends made by more swollen 
post ventral portion, males with pointed shells. 
Sex Length Height Diameter Locality 
Pec Solo ger xO niiny Maken Coutrany. Vot-. OSeDUa) 
Or 2 Xx 13 x I1imm_ (Pond, Columbia) 
Pesce Se a5) ks eTiesimn (lowes lL Contrary, ot. Josep) 
+) 145 -2-75°85- x 5.5mm (Singleton Lake, Halls) 
* 
rites 3S | EGY Se | torso, 4 a ces) 
The writer obtained about forty juveniles, within the range 
of the last two measurements, in shallow clear water along the 
northwest shore of Singleton Lake. They were confined to a small 
space and were traced here and there among a maze of tiny tracks. 
These juvenile shells differ from the adult by a thinner shell, more 
pointed posteriorly, a more greenish epidermis, more compressed, 
and by a coarser beak sculpture which, although arranged the same 
in its concentric bars curved up posteriorly, yet they extend down 
well on the center of the disk. (See Pl. III, fig. 8c). 
MISCELLANEOUS REMARKS:—The writer is able to bear out the 
statements of Drs. Sterki and Ortmann that parva ts locally herma- 
phroditic. In the past three years, hundreds have been collected 
in nearly all the Northwest Missouri lakes and streams, but not 
a single one has been found without the marsupial character of 
gills and the sexually dimorphic female shell. However, the male 
and female shells appear in Central Missouri. In all specimens 
'.* This symbol (*) would indicate hermaphroditism here. 
