PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 605 
Anastrophia ? hemiplicata WINCHELL and ScuucHERT, Geol. Minnesota, vol. 3, p. 382, pl. 30, 
figs. 29-31, 1893. 
This name is revived for specimens from the Prosser limestone commonly re- 
ferred to P. hemiplicata Hall. All the specimens from Minnesota, Wisconsin, 
and Iowa in the National Collections referred to Hall’s name are clearly a differ- 
ent species from the New York one. Winchell and Schuchert mention that their 
specimens differ from New York examples “in having the umbo of the dorsal 
valve more tumid and elevated beyond that of the ventral valve. The transverse 
diameter in the former [Minnesota specimens] is also shorter, while the indi- 
viduals are commonly smaller than those from eastern localities.” 
A fine specimen in the National Collections (24209) labeled Camarella bernen- 
sis by C. W. Hall indicates a more circular species than P. hemiplicata in its 
present average form. Hall’s label further states that ‘The type is from Berne, 
Minn.—It is unfortunately an immature specimen a little distorted.” 
It is evident from the few specimens in the National Museum that P. bernensts, 
like other species of the genus, is also a very variable species. These species to be 
satisfactorily delimited will have to be restudied on the basis of large collections. 
PARASTROPHINA BILOBATA Cooper, new species 
Plate 118, D, figures 30-44; plate 119, A, figures 1-5 
Shell small, subcircular outline; valves nearly equal in depth; sides rounded ; 
anterior margin indented medianly ; anterior commissure broadly uniplicate ; lat- 
eral commissure straight ; surface paucicostate, with 3 or 4 costae in the sulcus, 
3 or 4 on the fold, and about 3 on the flanks. 
Pedicle valve unevenly convex in lateral profile, the posterior quarter moder- 
ately convex in the umbonal region, the median half nearly flat and the anterior 
half moderately convex; anterior profile broadly and gently convex and with 
moderately steeply sloping lateral slopes. Umbonal region and area just anterior 
to it strongly swollen; sulcus originating at the middle, shallow and narrow but 
deepening suddenly near the anterior margin. Sulcus with a median trough 
forming the deepest part and flanked by costae which are depressed below the 
strong, narrowly rounded costae bounding the sulcus. Tongue short, truncated. 
Interior with wide and deep spondylium supported by a short, stout median 
septum. 
Brachial valve fairly evenly and moderately convex in lateral profile ; anterior 
profile broadly convex with the top somewhat flattened and steeply descending 
sides; fold originating at about the middle, low and indistinct throughout its 
length ; median part of fold depressed into a narrow and moderately deep sulcus 
containing a single costa; anterior of fold deeply indented by above-mentioned 
median sulcus and forming the deep emargination characteristic of the species. 
Flanks inflated and with steep slopes. Interior with narrow and deep notothyrial 
cavity ; cruralium elongate, septum short; brachiophores short; alate plates well 
developed ; supporting plates often thickened particularly at or near junction with 
alate plates. Adductor field elongate; posterior pair of adductor scars small, an- 
