ORDOVICIAN FAUNAS. 15% 
SCENIDIUM ANTHONENSIS Sard. 
Plate X., Figs. 5-7. 
1892. Scenidium anthonensis Sardeson, Bull Minn. Acad. Nat. Sci., 
vol. III., p. 333, pl. 4, fig. 7. i 
1893. Scenidium anthonensis Winchell and Schuchert, Pal. Minn., 
pt. L., p. 381, pl. 30, figs. 20-23. 
Description.—Shell small, subsemi-circular in outline, the greatest 
width along the hinge-line. Hach valve marked by from twenty to 
twenty-six simple, rounded plications. Pedicle valve subpyramidal, 
the beak erect; cardinal area large, flat, broadly triangular, with 2 
large delthyrium. Along the median line a slight elevation or ili- 
defined fold is developed. In the interior of the apical portion of 
the valve is a small spondylium. Brachial valve depressed, convex, 
with a slight mesial sinus. : 
The dimensions of an average specimen are: length, 2.5 mm., and 
breadth, 5 mm. 
Remarks.—This species has been only rarely observed, and is re- 
stricted to the lower portion of the Trenton formation, which 1s of 
Black River age or older. : 
CAMARELLA INORNATA Nl. Sp. 
Plate X., Figs. 8-10. 
Description.—Shell subovate in outline, lenticular or subglobose, 
with subequally convex valves, varying from longer than broad to 
broader than long. Surface nearly smooth, marked only by fine, in- 
conspicuous, concentric lines of growth. Pedicle valve with a pointed, 
incurved beak; the sinus originating near the middle of the valve and 
deepening towards the anterior margin. Brachial valve quite regu- 
larly convex, with little or no mesial elevation, even having a slight 
sinus towards the front in some individuals. 
The dimensions of a rather large individual are: length, 15 mm..; 
breadth, 15 mm.; thickness, 9 mm. Another individual: length, 10 
mm.; breadth, 10.4 mm.; thickness, 7.2 mm. Another pedicle valve: © 
length, 14 mm.; breadth, 16 mm. 
