New and Little Known American Paleozoic Ostracoda. 177 
examples having the typical shape. Figs. 64, c, d, represent three 
views of a complete carapace of the average size. As usual this 
specimen shows not even a trace of either the eye tubercle or 
muscle spot. It shows clearly that the right valve overlaps the 
left all around the free margins, and that there is no flange at the 
margin of the left valve, and only a very inconspicuous one at the 
ends of the right. Fig. 6a is the largest right valve seen. In this 
a very faint tubercle may be noticed. 
This species is restricted to the uppermost layers of the Cincin- 
nati group, and is exceedingly abundant at several localities. The 
best specimens seen I collected in Indian Kentuck creek, seven 
miles above Madison, Ind. 
Variety FRANKFORTENSIS, n. var. 
Under this name I propose to distinguish a form that is abundant 
in the gastropoda bed at the top of the Trenton at Reservoir Hill, 
Frankfort, and other localities in central Kentucky. In size and 
general appearance the variety is identical with the typical Indiana 
examples of Z. cecigena, but slight differences in the shape and in 
other respects, but more especially the fact that the form will be 
found of use in identifying this important horizon, induce me to 
distinguish it as above. A careful comparison with the typical 
form of the species (see Pl. XI, figs. 62-62) shows that the variety 
has the dorsal angles sharper, an appreciably flattened border or 
flange at the ends of doth valves, and the ventral edge a trifle more 
convex. The eye tubercle, and not infrequently the reticulated 
spot as well, is, though always very small, generally distinguishable. 
The outline is intermediate between figs. 52 and 6a of plate XI. 
ISOCHILINA SUBNODOSA, N. sp. 
eam ed. Liss. 7 a, b, C. 
Size: Length, 8.0 mm.; height, 4.7 mm ; thickness (left valve 
only), 1.7 mm. A very large but imperfect right valve has a 
length of 13.5 mm. 
Carapace oblong, subelliptical; ends subequal, rather narrowly 
rounded, most prominent about in the middle of the height. 
Dorsal margin straight, at least two-thirds as long as greatest length 
of valve; extremities sub-angular. Flattened border very wide 
but not sharply defined at the posterior end, about half as wide 
