PARTI CHAZYAN AND RELATED BRACHIOPODS—COOPER 109g 
Glenwood member of Platteville formation—This member consists of green- 
ish shale and ranges in thickness from 0 to Io feet but is generally from 4 to 6 
feet thick. This formation, like the St. Peter below it, is widespread and may 
be of different age in different places. In the bluffs on the Mississippi River, 
Minneapolis, thin layers of dolomite in the green shale produced a few fossils 
that ally it with the overlying Platteville: Campylorthis deflecta (Conrad). 
Templeton and Willman (1952, p. 6) state that the equivalents of the Glen- 
wood attain a thickness of 400 feet. 
Pecatonica member of Platteville formation.—This is the Lower Buff division 
of the early reports. It consists of dense, blue, buff-weathering, heavy-bedded 
magnesian limestone or dolomite. This member succeeds the Glenwood in north- 
ern Illinois, southwestern Wisconsin, and northeastern Iowa. Its maximum 
thickness, about 30 feet, is in Illinois and it thins to disappearance to the north. 
Few fossils have been listed, mostly Mollusca. 
McGregor member of Platteville formation—tThis term was proposed by Kay 
(1935, p- 286) to include the “Blue beds” and “Upper Buff” beds of the older 
reports. In Minnesota the Vanuxemia bed is partially equivalent to the “Blue 
beds.” The brachiopods listed for the McGregor in Minnesota are: 
Acanthocrania granulosa (N. H. Winchell) 
Crania setigera Hall = Acanthocrania setigera (Hall) 
Lingula elderi Whitfield = Pachyglossa elderi (Whitfield) 
Orthis tricenaria Conrad = Hesperorthis concava Cooper 
O. (Dalmanella) subaequata Conrad (not seen) 
O. (D.) subaequata conradi N. H. Winchell = Pionodema conradi (N. H. Winchell) 
O. (D.) subaequata perveta Conrad = Doleroides pervetus (Conrad) 
O. (Dinorthis) deflecta Conrad = Campylorthis deflecta (Conrad) 
O. (Hebertella) bellarugosa Conrad (not seen) 
Petrocrania dixonensis Cooper 
Rafinesquina minnesotensis N. H. Winchell = Opikina minnesotensis (N. H. Winchell) 
Rhynchotrema minnesotensis Sardeson = Rostricellula minnesotensis (Sardeson) 
Siphonotreta ? minnesotensis Hall 
Skenidioides anthonensis (Sardeson) 
Sowerbyella sp. 
Strophomena incurvata (Shepard) = S. plattinensis Fenton 
S. plattinensis crassa Raasch 
Trematis huronensis ? Billings 
Trigrammaria winchelli (Hall and Clarke) 
*Zygospira recurvisrostris (Hall) 
Z. (Hallina) nicolleti Winchell and Schuchert = Protozyga nicolleti (Winchell and 
Schuchert) 
Stauffer and Thiel (1941, p. 77) state that although remnants of the Peca- 
tonica and Magnolia members appear in Minnesota, they are not sufficiently 
clear to separate, and therefore the term “McGregor” as defined by Kay is pre- 
ferred. Bays and Raasch (1935, p. 298) excluded the “Upper Buff” beds from 
the McGregor and proposed Magnolia for them and other overlying beds. Bays 
(1938, p. 269) rejected McGregor and recognized Mifflin and Magnolia above 
the Pecatonica. Satisfactory faunal lists have never been published for these 
members. 
