PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 631 
Pedicle valve with nearly flat lateral profile in which the umbonal region is 
slightly inflated; anterior profile very gently convex. Sulcus originating 4 to 
6 mm. anterior to the beak. Sulcus deep at the front; tongue long and narrow. 
Flanks flattened and gently sloping to the margins. 
Brachial valve fairly evenly convex in lateral profile but the convexity gentle 
and most marked on the fold; anterior profile moderately strongly arched. Um- 
bonal region swollen but medially sulcate for a short distance; fold narrow and 
high, especially at the front end. Costation of fold variable, costae often appear- 
ing on sides of fold. Flanks well rounded and steeply sloping to the margins. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
SEA AE UNO ate as wk a arta. ute Me 13.4 12.2 16.0 9.0 
Patdtype MUlT72E2D) aos «care es. < 10.7 9.5 13.6 ra 
¥ ye 13.5 12.2 17.0 15.2 
ligated) raise. eels ILS 10.4 13.0 6.9 
Types.—Holotype: 117212a; figured paratypes: 117212b,d, 117213a,b; un- 
figured paratype: 1172I2c. 
Horizon and locality——Prosser formation (Zygospira bed) in Minnesota: 
At St. Anthony’s Hill, St. Paul; Kenyon, Goodhue County; Cannon Falls, 
Goodhue County ; and Warsaw, Rice County. 
Discussion.—This species may be recognized by its fairly narrow and fairly 
strongly elevated fold, erect beak, and depressed flanks of the brachial valve. This 
combination of features is quite unlike those of any other species described herein. 
The species somewhat resembles R. pulchra, but that species has a wider and 
lower fold and the flanks are not depressed. 
ROSTRICELLULA AINSLIEI (N. H. Winchell) 
Plate 135, A, figures 1-7; plate 138, E, figure 39 
Rhynchonella ainsliei N. H. W1ncHELL, 14th Ann. Rep. Geol. Nat. Hist. Surv. Minnesota, 
p. 315, pl. 2, figs. 5, 6, 1886. 
Rhynchotrema ainsliei (Winchell) WINCHELL and ScHucHERT, Geol. Minnesota, vol. 3, p. 459, 
pl. 34, figs. 1-8, 1895. 
A specimen of the brachial valve shows the typical cardinalia of Rostricellula 
having very long brachial processes and no cardinal process. The exterior is 
marked by fine, crowded, concentric lines of fine pustules. 
This species is characterized by its transverse form, evenness of its costae, and 
the well-rounded lateral margins. In these respects it differs from other described 
species except R. rotunda. From that species it differs in its larger size and 
proportions. 
Measurements in mm.—Hypotype (24866a), length 13.5, brachial length 12.5, 
width 18.0, thickness 10.3. 
Types.—Figured hypotypes: 24866a, 48943a. 
Horizon and locality—Decorah formation (Spechts Ferry member—Sticto- 
porella bed), Minneapolis, west St. Paul, Minnesota. Decorah formation, Chat- 
field, Fillmore County; Fountain, Fillmore County; Elmira, Olmstead County. 
