104 THE AMERICAN MIDLAND NATURALIST 
for intermediate forms not only for Fusconaia, but for other Genera 
of this Sub-family, Unioninae, especially. All Fusconaia of this 
State are strictly fluviatile. For the most part the Species of this 
Genus are hermaphroditic, for all localities. 
Fusconaia undata (Barnes). 
(O7E Pigtoe?s) 
Pl. x0; Figs: 20 AvandsB.. . 
1823— Unto undatus Barnes, Am. Jour. Sci., VI, p. 121, pl., 1V, fig. 4. 
1831— Unto trigonus Lea, Tr. Am. Phil. Soc., IV, p. 110, pl XVI, fig. 40. 
1900b— Quadr ula trigona, Simpson, Proc. U.S. Nat. Mus., XXII, p.,787. 
1900—Quadrula undata Walker, Nautilus, XXIV, pp. 5-11 and 16-24, 
Plates I and I. 
1912b— Fusconia undata (Barnes) Ortmann An. Car. Mus., VIII, p. 241. 
ANIMAL CHARACTERS. 
NUTRITIVE STRUCTURES—Branchial opening with short 
brownish papillae; anal slightly papillose, separated from supra- 
anal by very short,—even deciduous—mantle connection; i:ner 
gills larger, inner laminae free from visceral mass; outer gill 
undulate antero-ventrad, palpi moderately large, connected over 
half of their length antero-dorsad; most of soft parts yellowish 
or cream colored. 
REPRODUCTIVE STRUCTURES:—Marsupia formed by all four 
gills, when charged not distended, lumen of ovisacs subcylindrical; 
conglutinates same form, light red—even to white—according 
to age of embryos; glochidium semicircular, medium size, hinge 
line nearly straight, length and height, (0.160 x 0.155mm), about 
same. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell trigonal, thick, heavy anteri- 
orly, disk smooth; beaks high, full, pitched slightly beyond 
anterior end, sculptured with concentric ridges breaking into 
nodules at base of prominent umbonal ridge; dorsal line bowed, 
post-ventral line with long gentle incurve; broad shallow valley 
in front of post-umbonal ridge; ventral margin bowed in semi- 
circular form; epidermis greenish to rusty brown or black or 
mingling of both green and black; rest lines furrowed giving an 
undulated effect; post-umbonal ridge prominent. 
INTERNAL STRUCTURES:—Cardinals single and pyramidal in 
right, double and roughly socketed in left; laterals: double in 
