NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA — GRANT 47 



Table 2. — Measurements of Atribonium cooperorum from the Bell Shale, quarry 

 of Michigan Limestone and Chemical Co., Calcite, east of Rogers City, 

 Presque Isle County, Mich. 



Measurements, in millimeters 



ridges. It most nearly resembles A. simatum n. sp. from the lower part 

 of Alpena Limestone, differing from that species in its more pentagonal 

 than trigonal outline, rounded or nearly flattened but not actually flat 

 or emarginate anterior surface, its fewer costae on the fold, and its 

 more prominent fold. It is thinner than A. pingue n. sp. from the Four 

 Mile Dam Formation, and also has stronger, more numerous costae on 

 fold and flanks, has a more strongly curved pedicle beak and more 

 prominent fold, attains larger size, and is less convex. The height of 

 the fold recalls that of A. rhomboidale (of Fagerstrom) and A. halli 

 (Fagerstrom), but A. cooperorum has lower, narrower, and more 

 numerous costae on fold and flanks, and a much wider, less elongate 

 outline. 



Occurrence and abundance. — USNM loc. 31c, Bell Shale, in quarry 

 of Michigan Limestone and Chemical Co. at Calcite, east of Rogers 

 City, Presque Isle County, Mich. (44 specimens USNM 141826, 

 141834, 141835) ; USNM loc. 31h, Bell Shale in same quarry, NE. 

 side of railroad track, in shale dump (11 specimens USNM 141827) ; 

 USNM loc. 31, Bell Shale in sink, same quarry, sec. 36, T-34-N, 

 R-6-E, (3 specimens USNM 141828) ; USNM loc. 38e, lower part 

 of Ferron Point Formation, in quarry at Rockport, northeast corner, 

 Alpena County, Mich. (1 specimen USNM 141829, aff. A. cooper- 

 orum) ; Ferron Point Formation, uppermost beds in quarry at Rock- 

 port, Mich. (3 specimens USNM 141830, aff. A. cooperorum) ; Fer- 

 ron Point Formation (bed D), south end Black Lake, NW.^, SW.J4, 

 sec. 7, T-35-N-R-2-E, Presque Isle County, Mich. (1 specimen 

 USNM 141831, aff. A. cooperorum) ; lower part of Ferron Point, sink 

 in Rogers City Limestone, NW.J4, SW.J4, sec. 21, T-35-N-R-6-E, 

 Adams Point, Presque Isle County, Mich. (2 specimens USNM 

 141832, 141833, between A. cooperorum and A. simatum) . 



Age. — Early Middle Devonian. 



