200 
AUG. F. FOERSTE 
valve. In one specimen there is a slight tendency toward the 
elevation of the anterior snlcus of the brachial valve along its 
median line, and from this it is assumed that the anterior part 
of the median elevation of the pedicel valve might be slightly de- 
pressed along its median line, but neither tendency finds suffi- 
cient expression in any of the specimens at hand to admit of 
positive observation. Protozeuga sulcocarinata Savage, from the 
Alexandrian (Medinan) of Illinois and Missouri, appears closely 
related to the Anticosti form. The Plattin species, here under 
consideration, is supposed to be identical with the Black River 
species Zygospira nicolleti^ which was described originally under 
Hallina. 
10. Rafinesquina deltoidea Conrad 
Plate XXI, figs. 2, 2; plate XXII, figs. 2, 3. 
The small specimens of Rafinesquina, here identified as Rafin- 
esquina deltoidea (fig. 3), are not distinctly deltoid in form, but 
they correspond most nearly to the specimen figured by Hall and 
Clarke under that name (Pal. New York, 8, pt. 1, 1892, pi. 9A, 
figs. 1, 2), from the Trenton at Jacksonburg, New York. Most 
of these specimens do not exceed 20 mm. in length, but are so 
strongly convex as to indicate their full maturity. Abundant at 
localities 3 and 4 in the Kimmswick limestone of the Sanders 
Creek section. 
A single valve (fig. 2) , from locality 4 of the same section, re- 
sembles the specimen figured by Hall as Leptaena (= Rafines- 
quina) deltoidea (Pal. New York, 1, 1847, pi. 31 A, fig. 3a), from 
the Trenton limestone at Trenton Falls, New York. It is 28 
mm. long, 27 mm. wide, and has a convexity of 9 mm. 
Larger, and relatively less convex shells, such as those usually 
identified as Rafinesquina alternata (Emmons), also occur at 
locality 3 on Sanders branch. One specimen is 31 mm. long, 35 
mm. wide, and has a convexity of 7 mm. ; in other specimens the 
convexity is even less. 
All specimens of Rafinesquina alternata from the Plattin lime- 
stone of Ralls County are only moderately convex, the convexity 
usually not exceeding 4 mm. 
