Neir Lower Sihtnarh Osti'.dcocla. — Ufrich. 269 
prooosses. At tlie ends the intervals between these processes is 
about 0.1 mm., but in the central part of the ventral edge the}' 
are shortei'. and the projections themselves probal)ly not "so long. 
Tlie peculiar fringe distinguishes this species from all the others 
now referred to Lcperdifia. 
Formation und locality: Only one valve of this species is known. It 
Avas collected by the author in the upper beds of the Cincinnati or Hud- 
son River group, near Spring Valley, Minnesota. 
Schmidtella, n. gen. 
Carapace small, rounded, moderately convex. Valves intlated 
in the dorsal region so that this part projects shoulder-like over 
and out from the nearly straight hinge line. Right valve slightly 
the larger, its ventral edge overlapping that of the left. No 
sulcus nor tubercles. 
Type: SchmidteUa crassiinarglnata, n. sp. 
I am somewhat in doubt respecting the sj'stematic position of 
this genus, but provisionally would place it near Ap<i nliites. 
Jones, among the Leperditiidn-. Nor am I satisfied that the de- 
scription should not be modified so as to include several smaller, 
as yet undescribed, s}>ecies which agree in all other respects except 
in having an obscure subcentral impression. 
The name is given in recognition of the valuable services 
rendered to Silurian paleontology by Dr. F. Schmidt, of St. 
Petersburg, Russia. 
Schmidtella crassimarg-inata, n. sp. 
Plate IX, Figs. 27 to 30. 
I^ength, of an average right valve, 1.35 mm.; hight 1.0 mm.; greatest 
thickness 0,4 mm. 
Valves broad-oval, very slightly oblique, the ends almost equal, 
the lower half with the ventral margin curved to form somewhat 
less than a semicircle. Dorsal region flattened, slightly convex in 
aside view, rising very abruptly from and projecting slightly over 
the nearly straight hinge line. Point of greatest convexity above 
the center. An undefined but rather conspicuous broad furrow 
around the ends and ventral margin, least distinct posteriorly, 
p.roduces the thick border that has suggested the specific 
name. 
The obscurely defined, heavy and wide umrgin. :iiid the fiat 
