878 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Discussion—This is a rare species in the Oranda formation and is distin- 
guished by the strong anterior radial plication. The species is similar to F. sco- 
fieldi (Winchell and Schuchert) but differs in being somewhat wider, in having 
somewhat finer ornamentation, more prominent development of the radial plica- 
tion, and a smaller pedicle muscle area. Furcitella scofieldi has the radial plica- 
tions seen in the Oranda species, but not one of the specimens in the National 
Collection has this feature as strongly developed as the Virginia specimens. 
FURCITELLA SCOFIELDI (Winchell and Schuchert) 
Plate 229, A, figures 1-5; plate 265, C, figures 5, 6 
Strophomena scofieldi WINCHELL and ScHUCHERT, Amer. Geol., vol. 9, p. 286, Apr. 1, 1892; 
Geol. Minnesota, vol. 3, pt. 1, p. 398, pl. 31, figs. 18-21, 1895. 
Streptorhynchus subsulcatum SArRDESON, Minnesota Acad. Nat. Sci., Bull. 3, p. 335, pl. 4, 
fig. 39, Apr. 9, 1892. 
This species has been well described by Winchell and Schuchert, but no men- 
tion was made of the tendency of some specimens to show obscure plication 
which undulates the anterior parts. Mention is made of the bifurcation of the 
median ridge which is one of the distinguishing characters of this shell. 
Types.—Hypotypes: 117748, 117749a,b. 
Horizon and locality——Prosser formation (Zygospira and Vellamo | Clitam- 
bonites|] beds) in Minnesota: At Cannon Falls, Goodhue County; Kenyon, 
Goodhue County; road cut 1.2 miles east of U. S. Highway 52, on south edge of 
Cannon Falls, Goodhue County; St. Paul; 11 miles southeast of Kasson, Dodge 
County; County Highway O, $ mile south of U. S. Highway 14, 14 miles east 
of Eyota, Olmsted County. 
Genus MICROTRYPA Wilson, 1945 
Microtrypa Wiuson, Trans. Roy. Soc. Canada, ser. 3, vol. 30, sec. 4, p. 144, 1945; Geol. Surv. 
Canada, Bull. 8, p. 111, 1946. 
Microtrypa is characterized as “semicircular or subtriangular in outline; has 
a low evenly convex brachial and a resupinate pedicle valve, concave on the an- 
terior part ; a small round pedicle muscle scar and four septa in the brachial valve. 
The median septum is forked anteriorly and two laterals added, which do not 
curve as in Trigrammaria. The two limbs of the bifurcated median septum are 
subparallel, the two lateral septa are divergent. Thus the brachial interior arrives 
at the same septal system as Opikinella of the Rafinesquina group, though the 
convexity of the valve is reversed. The [pseudo] punctae of the intermediate 
shell layer form a fine, unorganized network. 
“Microtrypa differs from Trigrammaria in its low, even convexity, its general 
lack of a fold in the brachial valve, and in having 4 subparallel septa in the 
brachial valve instead of 3.” 
Microtrypa resembles Furcitella in some details, especially in the forking of 
the median ridge. Furcitella, however, is not as markedly resupinate as Micro- 
irypa, indeed it is generally biconvex in profile but with the brachial umbo flat- 
tened or slightly concave. 
