THE NAIADES OF MISSOURI 391 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell large broadly elliptical, solid 
alated post-dorsad; somewhat inflated at middle of disk, beaks 
low sculptured concentrically and also double-looped; disk not 
sculptured; epidermis usually black-reddish with broad rays in 
young specimens; female shelJs blunt, or even truncate, vertically 
for its posterior end. 
INTERNAL STRUCTURES:—Cardinals erect-double in both 
valves; laterals also double placed at an upward angle; beak 
cavities moderately deep; nacre usually purple. 
Sex Length Height Diameter Locality 
OMS 6. ex Li | we SOLS (Platte, R., Dixon Falls) 
CaS On exe Dex) 5 a5O (eae Platten eity) 
OPe IRA ee Se oe) Oe LS oO (Osage R., Warsaw) 
OF SSR Re sax YoGio (Grand R., Utica) 
MISCELLANEOUS REMARKS:—This species is most typical in 
North Missouri; the shell is thinner, smaller and rather dwarfed 
in Central Missouri and is wholly lacking in South Missouri 
drainage. The writer has only found alata lacustrine on one 
occasion, but that may have been due to accidental translocation. 
Breeding records show it to be bradytictic. The writer has observed 
that most marsupia of this species, when gravid with ripe glochidia, 
have purplish blotched marsupia; this character, however, is 
rather inconstant. Alata has a general distribution throughout 
the Mississippi and St. Lawrence River basins. 
Proptera purpurata (lamarck). 
(“Purple Shell,’ ‘‘ Purply,’”’ ‘‘ Buttermilk Shell,’’ Red Shell.’’) 
Pl. XXVI, Fags. 92 A—D. 
1819—Umio purpurata Lamack, An. Sans, Vert., VI, p. 71. 
t900b—Lampsilis purpuratus Smpson, Pr. U. S. Nat. Mus., XXII, 
p. 568. 
1912b—-Proptera purpurata (Lam.) Ortmann, An. Car. Mus., VIII, 
Pp. 234. 
ANIMAL CHARACTERS. 
NUTRITIVE CHARACTERS:—lIdentical with those of alata. 
REPRODUCTIVE STRUCTURES:—Marsupium consists of twenty 
ovisacs placed in posterior half of outer gills; glochidia (according 
to Lea) ax-head shape—no measurement given. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES :—Shell large, rather elongate—ellip- 
