BRACHIOPODA. 453 
Orthis (Dalmanellu) amcena.] 
Vairety circularis is distinguished by its subcircular outline, usually smaller size 
and very fine, equal and more numerous striz, a greater number of which terminate 
on the cardinal line. The tubulose character of the striz is also developed, but it 
is never a conspicuous feature. Occasionally specimens will be found with very fine 
strize, which are, however, larger and wider than is usual in this variety. 
O. subequata, var. circularis, attains its maximum development in individuals in 
the “Glade limestone” in Tennessee, and is there somewhat coarser in its strie. 
Formation and locality.—Not rare in the upper part of the Trenton shales at Minneapolis, St. Paul, 
Cannon Falls, Rochester and Fountain, Minnesota. Rare near the top of the Birdseye limestone two 
miles south of High Bridge, Kentucky. Common in the ‘‘Glade limestone” at Lebanon and elsewhere 
in middle Tennessee. 
Collectors.—W. H. Scofield, E. O. Ulrich and the writers. 
Mus. Reg. Nos. 279, 346, 3515, 4049, 4935, 5149, 6778, 6804. 
Ortuis (DALMANELLA) AamM@NnA N, H. Winchell. 
PLATE XXXIII, FIGS. 48 and 49, 
1880. Orthis amena N. H. WINCHELL. LHighth Annual Report of the Geological and Natural 
History Survey of Minnesota, p. 65. 
Original description: “Shell transversely oval with a hinge-line that compares 
to the greatest diameter about as five to nine. Evenly rounded from the cardinal 
extremities, which hardly disturb the symmetry of the outline, through the front 
margin; valves nearly equal; umbonal region of the receiving [ventral] valve sur- 
rounded by a depressed or somewhat concave border, which in the front margin 
becomes flat or inclines toward the entering [dorsal] valve; the entering valve having 
a much less marginal concavity, but being moderately and evenly convex; cardinal 
areas small; foramen [delthyrium] also small; beak of the receiving valve somewhat 
incurved; that of the entering valve small, but abrupt and distinct, surface marked 
by rays which are doubled or tripled in number on the umbo by implantation, but 
maintain a larger size than the rest in passing to the margin, several of which are 
also curved so as to run out in the hinge-line; transverse diameter, nine to ten lines; 
perpendicular diameter from seven and a half to eight and a half lines. Interior 
unknown.” — 
Two somewhat compressed type specimens are the only ones known of this 
species. They differ but slightly from O. subequata, as the strive which originate 
on the umbo increase in prominence to the anterior margin, between which are two 
or three smaller ones. A very similar striation is seen in O. (D.) stonensis Safford, a 
species also belonging to the O. subequata section, but always smaller and narrower 
than O. amena Winchell. 
