io THE AMERICAN MIDLAND NATURALIST 
Length 28 Height 18 ~ Diameter 14 
73 20 18 
60 35 2 
73 37 22 
84 43 30 
QUADRULA UNDULATA (Barnes). 
Unio undulatus Barnes, Am. i Scr aVier8225 pe neo wp de 
Margarita (Unio) undulatus Lea, Syn., 1836, p. 12; 1838, p. 14. 
Mya undulata Eaton, Zool. Text-Book, 1826, p. 219. 
Unio undulata Valenciennes, Rec. Obs. Zool. Anat, II, 1833, p. 229, pl. 
WIE west 2eiea'ar sail. 
Quadrula undulata Baker, Moll. Chi., Pt. I, 1898, p. 82, pl. X XII, fig. 1, 2. 
Crenodonta undulata Ortmann, Ann. Car. Mus. VIII, 1912, p. 246. 
Unio costaius Conrad, Monog., II, 1836, p. 17. pl. VII. 
Plectomerus costatus Conrad, Proc. Acad. N. Sci. Phila., VI, 1853, p. 260. 
Unio plicatus Kuster, Conch. Cab., 1856, p. 137, pl. XL, fig. 3. 
Unio atrocostatus Sowerby, Conch. Icon., XVI, 1868, pl. LX XVII, fig. 404. 
This is a very heavy shell, somewhat elongated and irregularly 
rhomboid in outline. A characteristic feature of this species is the 
sculpture consisting of five strong ridges that are swollen where 
they cross the posterior ridge. There are oblique folds on the 
posterior portion of the disk; they run nearly parallel with the 
posterior ridge and are sometimes broken into corrugations or 
pustules. The epidermis is greenish or yellowish green in young 
specimens; in old specimens the color changes to dark brown or 
black. The dorsal margin is straight; the ventral margin is slightly 
rounded. ‘The lines of growth are often raised into thin scales 
on the ventral border. The cardinal teeth are double in both 
valves, equal in the left, and the anterior much smaller in the right 
valve. All the teeth except the anterior in the right valve are 
heavy thick, triangular, striated and grooved. ‘The lateral teeth 
are long, thick, curved ventrally and serrated. The pallial line is 
deeply impressed throughout. The cavity of the beaks is broad and 
shallow. The nacre is silvery white and iridescent on the posterior 
portion; some specimens show brown blotches. 
Length 64 Height 43 Diameter 23) 
SOW 55 30 
122 78 : 46 
112 74 43 
155 115 By) 
