PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 273 
slender, elevated radii and short concentric dashes forming the quadrangular pits, 
some of which appear opposite crossbars or opposite pits, patches of each oc- 
curring on the same shell. This feature is not unlike the ornamentation of 
T. foerste, but in that species the radial and concentric elements are not elevated, 
but are flattened. 
Some features of T. foerstei such as the ornamentation and size are sugges- 
tive of T. punctostriata Hall from the Saltillo limestone at Clifton, Tenn., but 
T. foerstei has more convex brachial valve, stronger ornamentation, and an 
unrestricted foramen. 
TREMATIS HURONENSIS Billings 
Trematis huronensis Butuincs, Geol. Surv. Canada, Paleozoic fossils, vol. 1, p. 53, fig. 59 
(adv. sheets 1862), 1865; Geol. Canada, p. 159, fig. 130, 1863—Lestey, Geol. Surv. 
Pennsylvania, Rep. P 4, p. 1198, figs., 1880. 
Horizon and locality.—Black River limestone, Pallideau Islands, Lake Huron. 
TREMATIS MINNEAPOLIS (Sardeson) 
Productella minneapolis SARDESON, Minnesota Acad. Nat. Sci., Bull. 3, p. 332, pl. 4, figs. 11, 
12, 1892. 
Trematis huronensis ScHucHERT (not Billings), Winchell and Schuchert, Geol. Minnesota, 
vol. 3, p. 368, fig. 29, 1893. 
Horizon and locality—Decorah formation (Spechts Ferry member-Sticto- 
porella bed), Minneapolis, Minn. 
TREMATIS PARVA Cooper, new species 
Plate 19, E, figures 12-14 
Species represented by three brachial valves only; small, broadly elliptical in 
outline; sides narrowly rounded, anterior margin broadly rounded. Gently con- 
vex in both profiles. Beak small, marginal, incurved. Umbo narrow, smooth, 
with a shallow sulcus originating at its anterior end; sulcus continued forward, 
widening gradually to the anterior margin. Posterolateral slopes to the margins 
steep. Lateral slopes moderately steep but anterior slope long and fairly gentle. 
Flanks bounding sulcus somewhat swollen. Surface marked by deep circular 
pits arranged in quincunx. 
Measurements in mm.—Holotype, length 3.7, width 4.7. 
Types.—Holotype: 109703; figured paratype: 109705a; unfigured paratype: 
109705b. 
Horizon and locality.—Chatham Hill formation in Virginia: Grayson Farm, 
north slope of Walker Mountain, 4 miles southwest of Bland, Bland County. 
Lower Whitesburg formation in Tennessee: 4 mile west of Bulls Gap, Bulls 
Gap (T.V.A. 171-SE) Quadrangle. 
Discussion—This species is characterized by its small size and the quincun- 
cial arrangement to the deep pits on the surface. The ornamentation is not quite 
like that of any other American species of the genus, and it is possible that the 
