266 The American Geologist. November, 1892 
pronounced. Groove in ventral edge- of left valve sharplj' defined. 
Surface with a broad, undefined mesial depression in the dorsal 
slope. This depression is as much stronger than the one in L. 
oiquilatera as it is weaker than the one in ]j. sulcata. 
Formation <(nil loadity: Same as the last One hundred specimens, or 
more. 
Leperditia g-ermana, n. sp. 
Plate ix, Figs. 16 to 18. 
Length of averaga left valve, 2.17 mm.; hight, 1.4 mm.; greatest thick- 
ness, 0.67 mm. 
This form is very closel}' related to L. mundula — perhaps it is 
merely a local variety of that species. It differs in having the 
ends more equal, the surface more convex in the dorsal half, and 
in having a very narrow rim or marginal channel, visible in a side 
view only, at the ends. Again, instead of a slight elevation sur- 
rounded by correspondingly gentle depressions, we have in L. 
germana only a sulcus. This is about as strong as the one in 
L. inflata, which species the present form resembles rather closely 
also in the outline. The basal line, however, is usually more con- 
vex and with the most prominent point nearer the center. But 
the most important difference lies in the lesser inflation of the 
posterior half of the dorsal region. (Compare Figs. 14 and 17, 
PI. IX.) 
Formation and locality: Associated with Schmidtella crassimavf/inata 
Ulrich, at Mineral Point, Wisconsin, where it occurs abundantly in some 
of the thin layers of the Birdseye or "Lower Blue" limestone. 
Leperditia sulcata, n. sp., and var.ventricornis, n.var. 
Plate ix, Figs. 19 to 23. 
Length of an average right valve, 2.1 mm.; hight, 1.38 mm.; thicliness, 
in anterior half, 0.48 mm., in posterior half, 0.58 mm. 
Valves sub-ovate, ends nearly equal, the posterior a little the 
widest; back straight for about three-fifths of the entire length; 
ventral edge gently convex, the most prominent part a little be- 
hind the center. Surface rising abruptly from all the edges ex- 
cept the dorsal which is occupied by the expanded terminus of a 
broad sulcus which, though shallow and of undefined limits, is, 
nevertheless, always a conspicuous feature of the valves. In a 
ventral view the profile is highest a short distance within the ends, 
while the central portion is at least straight and in most cases 
decidedly concave. Closure of valves as in L. injlata. 
This form may be regarded by some authors as nearer Primitia 
