THE NAIADES OF MISSOURI 194 
Pleurobema catillus (Conrad). 
(“White Pigtoe,-” ‘‘Pink Pig-toe,” ‘Solid Pig-toe.’’) 
Pier! thes." SOA Gd... 
1836— Unio catillus Conrad, Monog. III, p. 30, pl. XIII, fig. 2. 
1838— Unio solidus Lea, Pr. Am. Phil. Soc., VI, pl. V, fig. 13. 
1845—Unio fulgidus Lea, Pr. Am. Phil. Soc., p. 164; Tr. Am. Phil. 
SE Sevilla som apc jo) ONVAS akin mi(oy 
1900b—Quadrula solida Simpson, Pr. U. S. Nat. Mus., XXII, p. 789. 
ANIMAL CHARACTERS. 
NUTRITIVE STRUCTURES:—Branchial opening densely papil- 
lose; anal finely papillose; supra-anal closely connected to anal; 
gills rather long and wide, the inner being wider and longer, inner 
laminae free from visceral mass; palpi long and connected about 
two-thirds of their length antero-dorsad, soft parts tanned flesh- 
color, yellowish in front of branchial opening, papillae blackish. 
REPRODUCTIVE STRUCTURES ——Marsupia only occupying outer 
gills, ovisacs swollen more centro-lengthwise tapering obtusely 
at ventral edges; conglutinates leaf-like, compressed white; 
glochidia semicircular, medium in size, hinge line nearly straight; 
length and height equal (0.160 x xo.160mm.). 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:>—Shell subtriangular with obtusely 
pointed posterior end, very solid and thick through cardinal 
hinge region, ventral line always more curved than dorsal; disk 
smooth, post-umbonal ridge flattened; radial furrow in front 
rather shallow and wide; beaks full, protruding but not beyond 
anterior end; epidermis reddish brown with decided streaks of 
green radiating ventrad from umbonal region. 
INTERNAL STRUCTURES:—Cardinals heavy, double in both 
valves; laterals double in right, single in left valve; interdentum 
broad, short and thick; umbonal cavities shallow; nacre salmon 
to rosy pink. 
Sex Length Height Diameter Locality 
ofl) Io) (OL Poere bie (White R., Hollister) 
OF Son Ex OAle <A (Black R., Williamsville) 
Ct PSO MOS W ex AO (White R., Hollister) 
MISCELLANEOUS REMARKS:—Conrad’s catillus (described as 
sepatate from coccineus by the author, but united by Simpson) is 
