OSTRACODA. 639 
Leperditella dorsicornis ] 
LEPERDITELLA ? pDorsicornis Ulrich. 
PLATE XLY, FIGS. 19, 20 and 20a. 
Leperditia ? (Primitia) dorsicornis Utricn, 1892. American Geologist, vol. x, p. 267. 
SizeE.—(L. V.) Length 1.72 mm.; hight 1.1 mm.; thickness 0.54 mm. 
Valves subelliptical, slightly oblique, the ends subequal, the back straight nearly 
to the posterior extremity; the latter is generally convex and almost vertical in the 
upper two-thirds, while in the lower third the outline merges rapidly into the uni- 
formly convex basal margin; anterior end uniformly curved. Surface much the 
highest in the posterior half, with a part prolonged dorsally into a short and obtusely 
pointed prominence that bends down close to the hinge line and projects somewhat 
beyond it. This prominence gives definition to the posterior side of a distinct sulcus 
extending almost half across the valve from the central part of the dorsal edge, and 
forward along the latter. 
’ Though having a sulcus, and therefore agreeing in a general way with Primitia, 
I have chosen to arrange this species with Leperditella because it seems to represent 
merely an extreme development from such typical species of the genus as L. inflata, 
L. germana and L. sulcata. Specifically the present form is readily enough distin- 
guished by the concentration of the dorsal prominence, and greater definition of the 
sulcus. The form which I called Primitia glabra,* and which occurs in the upper 
beds of the Cincinnati group in Ohio and Indiana, has a similar outline, but it is 
somewhat smaller and without the dorsal prominence. Still, I would not be sur- 
prised to find that it has overlapping valves as in Leperditella. 
Formation and locality.—The type was found in the Hudson River shales at Savannah, Illinois. As 
equivalent strata occur near Wykoff and Spring Valley, Minnesota, it is quite likely that the species 
occurs also in this state. 
Genus SCHMIDTELLA Ulrich. 
Schmidtella, ULRICH, 1892. American Geologist, vol. x, p. 269. 
Carapace small (2 mm. or less in length), short, rounded or subovate, moderately 
convex, more or less inflated in the dorsal region, this part being the thickest and 
appearing generally (in an end view), as projecting shoulder-like over and out from 
the straight hinge line; right valve slightly larger than the left and overlapping it 
along the ventral margin. No eye tubercle nor sulcus, but a faint central pit and 
elevation occasionally present. 
Type; 8. crassimarginata, Ulrich. 
* Jour. Cin. Soc. Nat. Hist., vol. xiii, p. 184; 1890. 
