470 THE PALEONTOLOGY OF MINNESOTA. 
(Cyclospira bisuleata. 
In Zygospira, Glassia, Dayia and Atrypa of the Atrypide the primary lamelle 
diverge widely and have between them the spirals; but in the Spiriferidw, to which 
family Cyclospira belongs, the primary lamelle remain close together and they are 
between the spirals, except in Cyclospira. 
This type of calcareous brachial supports has heretofore not been known to 
occur in rocks older than the Upper Silurian, and it is therefore interesting to find 
a species possessing them so early as the Trenton of the Lower Silurian. In Upper 
Silurian genera of the family Spiriferide the number of revolutions in each spiral 
cone is always numerous, while in Cyclospira it never exceeds much more than two 
turns and is therefore more rudimentary. Since the primary lamelle remain straight 
where they join the crural plates in both Clyclospira and in the members of the 
family Spiriferide the genus must be regarded as belonging to that family. It is 
also geologically and structurally nearer the ancestral stock which gave origin to 
the entire suborder Helicopegmata, or spire bearing families. Zygospira, however, is 
still nearer this ancestral stock, since it is known to occur in the Birdseye and Black 
River formations; but in this genus the apices of the spirals are dorso-medially 
directed. The direction of coiling serves well enough for family distinction, but 
we believe that both types of spirals, and also the Terebratulide, were derived from 
one stock, which probably is to be looked for in the Rhynchonellide. Waagen,+ how- 
ever, derived the family Atrypide, of which Zygospira is a member, from the Rhyncho- 
nellide, while all the other forms of spire-bearing genera he considered as developed 
from the Terebratulide. 
CYCLOSPIRA BISULCATA Emmons, sp. ? 
PLATE XXXIV, FIGS. 49—54. 
1842. Orthis bisulcata EMMons. Geology of New York; Report, Second District, p. 396, fig. 4 (not® 
described). 
1847. Atrypa bisuleata HALL. Paleontology of New York, vol. i, p. 139, pl. xxxu1, fig. 3. 
1859. Genus ? bisuleata HALL. Twelfth Report, N. Y. State Cabinet of Natural History, p. 65. 
1877. Camarella bésulcata MILLER. American Paleozoic Fossils, p. 107. 
1892. Camarella owatonnensis SARDESON. Bulletin of the Minnesota Academy of Natural Sciences, 
vol. iii, p. 328, pl. rv, figs. 1-3. 
Original description: “Small, ovoid; dorsal [ventral] valve with a well defined, 
narrow, mesial sinus, which continues about halfway to the beak, and from there the 
center becomes much elevated; beak of the dorsal valve strongly incurved over that 
of the oposite valve; ventral [dorsal] valve depressed-convex, prominent on the umbo, 
beak very small and abruptly incurved; front with two short, well defined furrows, 
ending in two plications, which close on each side of the projecting plait formed by 
the extension of the mesial groove of the dorsal valve.” (Hall, op. cit.) 
+ Pal. Indica., ser. xiii, vol. i, p. 550, 
