THE NATURAL HISTORY SURVEY. 67 
* often reflected upward beneath the beak of the left valve, and 
one or two faint ridges in front of it on the right valve; laterals 
generally wanting. 
Animal: Anal opening minutely papillose or crenulated; 
inner gill wholly or in part united to the abdominal sac; outer 
gill of the female filled when gravid with ovisacs which run 
crosswise with it and which probably empty through the outer 
wall of the gill. (Simpson. ) 
9. Strophitus edentulus Say, pl. xii., figs. 3, 5, 6; pl. xvii., fig. 3. 
Alasmodonta edentula Say, New Harmony Disseminator, Vol. II., No. 22, 
p. 340, 1829. 
Anodonta tetragona LEA, Trans. Amer. Phil. Soc., 2d series, Vol. X., p. 
82, pl. viii., fig. 25, 1845. 
Anodonta shafferiana Lea, Trans. Amer. Phil. Soc., 2d series, Vol. X., p. 
288, pl. xxvi., fig. 56, 1852. 
Anodonta arkansasensis Lea, Trans. Amer. Phil. Soc., 2d series, Vol. X., 
p. 2738, pl. xxix., fig. 56, 1852. 
Alasmodonta rhombica ANTHONY, Amer. Journ. of Conch., Vol.I., p. 158, 
1865. 
Anodonta annulata Sows, REEVE, Conch, Icon., Vol. xvii., Anodon, pl. 
xviii., fig. 67, 1869. 
Shell; Rather solid, not much inflated, long-ovate or elliptical 
in form, rounded before and obtusely angled behind, dosal mar- 
gin slightly curved, ventral margin rounded; posterior margin 
obtusely rounded and posterior slope sometimes angulated; 
surface marked by strong lines of growth; umbones not much 
elevated, yellowish -brown in color, eroded in adult specimens, 
and marked by three very large and coarse ridges, and one or 
two less conspicuous ones; the apex of the umbo is directed 
anteriorly; ligament strong, dark brown in color; epidermis 
light horn or yellowish brown with wide rays of dark green on 
the lighter background; the rays disappear in old specimens 
which become almost black; hinge line near the umbones rein- 
forced by a tooth-like deposit which is a rudimentary cardinal 
tooth; adductor muscle scars, pallial line and protractor pedis 
muscle scar distinct but not impressed; dorsal muscle scars 
situated on the anterior face of the cavity of the beaks, the latter 
of medium depth; nacre bluish white, the cavity of the beaks and 
center of the shell, in some specimens, being strongly tinged 
with salmon; more or less iridescent. 
Length, 68.00; height, 43.00; breadth, 26.00 mill. (8052). 
o> eee ee. Oe ** 19:00. ‘'*),(9801). 
i 760.005. #4 4400; *' 29.00 ‘ (coll. Jensen). 
a 84,005 —F 45.00; ty 29.00 ‘* (12418). 
