116 THE AMERICAN MIDLAND NATURALIST 
of post-dorsal ridge few, broad, shallow and faint; epidermis leathery 
red to black, rarely yellowish or greenish. 
INTERNAL STRUCTURES:—Cardinals double in both valves; 
laterals single in right, double in left valve; umbonal cavities nar- 
rowly deep; muscle scars well impressed; nacre marble white 
with blue and old rose tints posteriorly; deep vein mark on antero- 
extra pallial border. 
Sex Length Height Diameter Localities. 
SorOn, exe Of xy Simin (Mississippi R., La Grange, Mo.) 
OW ea Xee Aor Xe aA Oma. (Osage R., Monegaw Springs, Mo.) 
One ds ont Aon eX) ZO. (Mississippi R., Hannibal, Mo.) 
CSUs Sek, 12CuL xn 2OKr. (Osage R., Osceola, Mo.) 
Juveniles of latter measurement very globose; epidermis 
olivaceous with a reddish brown band in center parallel to growth 
lines; post umbonal ridge rather prominent; one heavy undulation 
at post base with two heavy furrows on either side. The very 
greatly inflated beaks of adult shell is doubtless due to the globular 
shell of the juveniles. . 
MISCELLANEOUS REMARKS:—Amblema peruviana (Lam) is 
the Quadrula plicata (Say) of authors according to the recent 
decision of Mr. Bryant Walker who is making a special study 
of original Lamarckian types. Mr. Walker states that Say’s 
type of plicata came from Lake Erie and is the form that Lea 
describes as hippopaea and that peruviana is a form of the Ohio 
shell commonly called plicata but which is really the rarplicata 
Deshayes. This species should perhaps be reduced to the sub- 
species, ‘‘Amb. rariplicata peruviana (Lam); however, because 
of its difference from rariplicata in the possession of full beak 
and more globular juvenile shell it is left in specific rank. It is 
found in typical form in the Mississippi north of the Missouri, 
is scarce but rather typical in the Osage, but is not found at all 
in the interior north of the Missouri, River. 
Amblema rariplicata (Deshayes) 
(“Ohio Plicata,’’ ‘‘Few Ridge,” ‘Big Blue Point.’’) 
Pl. [X,—Fig. 20; Pl. XVI,—Figs. 36A-D. 
1830—Unio rariplicata Deshayes, Enc. Meth; II, p. 578; An. Sans. 
Vert., 2d. ed., VI, 1835, p. 533; 3d. ed., II, 1839, p. 667. 
ANIMAL CHARACTERS. 
Nutritive StrucrurESs:—-Branchial opening very long with 
short yellowish papillae; anal slightly crenulate; supra-anal very 
