606 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
terior pair elongate; median septum continued forward as a low median ridge 
anterior to the anterior end of the adductor field. 
Measurements in mm.—Holotype, length 4.4, brachial length 4.2, width 5.0, 
hinge width 1.6, thickness 3.0. 
Types.—Holotype: 117166b; figured paratypes: 117166a,c-f,h-j; unfigured 
paratype: 117166g. 
Horizon and locality.—Lower 3 feet of the Pratt Ferry formation in Alabama: 
0.2 mile southeast of Pratt Perry, Blocton (15’) Quadrangle. 
Discussion.—This species is quite unlike any other member of the genus yet 
described. It is the smallest species of the genus known, the largest specimen 
having a width slightly greater than 6 mm. It is particularly characterized by 
the anterior emargination produced by the sulcus within the median fold of the 
brachial valve. 
PARASTROPHINA HEMIPLICATA (Hall) 
Plate 106, G, figures 33-44; plate 117, D, figures 19-27 
Synonymy: For full synonymy of this species up to 1915, see R. S. Bassler, Bibliographic 
index of American Ordovician and Silurian fossils, U. S. Nat. Mus. Bull. 92, p. 945. When 
using this synonymy several citations should be excluded. One such is Anastrophia ? hemi- 
plicata Winchell and Schuchert. The citation under Parastrophia hemiplicata Schuchert, 
Proc. U. S. Nat. Mus., vol. 22, 1900, p. 158, refers to Baffin Land specimens that were 
described by S. K. Roy in 1941 as P. hemiplicata minor. Roy also determined the age of the 
beds in which these specimens occurred as late Ordovician. The references to Camerella 
bernensis should also be excluded. This seems to be a valid species (see above). 
The following references from 1915 to the present writing should be added: 
Camerelia hemiplicata (Hall) ScHucHERT and Cooper, Mem. Peabody Mus. Nat. Hist., 
vol. 4, pt. I, p. 168, pl. 25, figs. 3, 4, 6, 9-11, 16, 24, 43, 1932. 
Parastrophina hemiplicata (Hall) Kay, Bull. Geol. Soc. Amer., vol. 48, p. 330, pl. 9, (Hull), 
1937.—ST. JosEPH, Geol. Mag., vol. 78, No. 5, p. 377, text figs. 3-5, 1041. 
Moderately large, transversely subelliptical in outline ; valves of unequal depth, 
the brachial valve having the greater depth; posterolateral margins straight ; 
sides narrowly rounded ; anterior margin truncated ; anterior commissure unipli- 
cate; surface paucicostate, the fold having 3 to 5 costae, the sulcus 2 to 4, and 
the flanks 2 or 3. 
Pedicle valve gently convex in lateral profile ; anterior profile very broadly and 
gently convex; umbonal and median regions swollen; sulcus originating at the 
middle, wide, shallow, forming a short serrate tongue. Flanks somewhat swollen. 
Brachial valve moderately convex in lateral profile with the greatest convexity 
in the umbonal region. Anterior profile strongly bowed, with steep lateral slopes. 
Umbo and median region swollen; fold originating at the middle, low in some 
specimens with the median costae depressed slightly below those forming the 
outer margins of the fold; flanks swollen and with steep slopes. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Hypotype (117168b).......... 10.4 10.5 12.9 aie 8.0 
‘1 CTIF TOSS) HA Lis YG 10.9 10.8 12.9 24°? 8.5 
