BRACHIOPODA. 397 
Strophomena billingsi.] 
species, restricted to the Hudson River group, and takes the place of S. nutans 
of the Ohio valley, in the deposits of this formation on Anticosti and in Min- 
nesota. 
Formation and locality.—Common in the Hudson River group at Spring Valley, Wykoff and near 
Granger,, Minnesota: Anticosti. 
Collectors.—E. O. Ulrich, W, H. Seofield and the writers. Also in the collection of Dr. C. H. 
Robbins, of Wykoff, Minnesota. 
Mus. Reg. Nos. 232, 430, 4077, 8187, 8188. 
STROPHOMENA BILLINGSI ”. Sp. 
Fig. 32. Billings’ original illustration of Strophomena recta. a, side view; b, ventral view: 
ce, portion of face enlarged. : 
1862. Strophomena recta BILLINGS (non Conrad). Paleozoic Fossils, vol. i, p. 130, figs. 108a—108e, 
Original description: “Semielliptical, both valves nearly flat, hinge-line equal 
to, a little greater or a little less than, the width; sides somewhat straight for about 
half the length, and either parallel or slightly converging forwards; all of the front 
half of the shell uniformly rounded, sometimes only gently convex or somewhat 
straight in the middle of the front margin. Ventral valve slightly convex in the 
umbonal regon, and elsewhere flat or gently concave; beak scarcely distinct from 
the cardinal area, slightly depressed below the umbo; area of medium size, flat, 
extending the whole length of the shell, forming an obtuse angle of from 110° to 135° 
with the plane of the lateral margin; foramen triangular, width at the base greater 
than the hight, closed by a convex deltidium which does not quite reach the hinge- 
line, but has its lower margin concave. Dorsal valve uniformly very depressed 
convex or nearly flat, slightly concave at the cardinal angles and with a barely 
perceptible mesial depression along the middle, which commences very near the 
beak and extends one-third or one-half the length of the shell; beak very small and 
minutely elevated above the cardinal edge; area varying in size from less than one- 
half to nearly equal that of the ventral valve. ; 
“Surface with fine, rounded, slightly crenulated, radiating strize of different 
sizes, the smaller coming in by implantation at various distances from the beak. In 
some specimens the strie are more nearly of one uniform size than in others; at the 
front margin there are usually four of the larger and four or five of the smaller striz 
in the width of one line. When the surface is perfectly preserved it is seen to be 
