or 
OSTRACODA. 63! 
Leperditia fabulites.] 
right valve in which a row of minute puncte is generally distinguishable; overlap 
extending all around the free edges, strongest ventrally; except in rare instances, 
neither valve has a flange or flattened border, and when present it isin all cases very 
narrow and undefined; dorsal edge somewhat thickened, especially upon the left 
side. Surface of valves smooth or very faintly pitted, rather evenly convex 
with the greatest thickness somewhat beneath the center; a low ridge-like thicken- 
ing along the posterior half of the dorsal margin of the left valve is to be noticed. 
Eye tubercle just distinguishable in most cases, rarely so distinct as in the specimen 
figured, often not to be detected. On the inner surface however it is always marked 
by a distinct pit. Muscle spot not distinguishable externally except when the 
specimens are weathered, but on the inner side it is often well marked and surrounded 
by fine reticulating radial lines, short dorsally, longest ‘post-ventrally. On the 
inner side of the ventral edge of the right valve there are two rows of small papille, 
three to five in each, the number seeming to increase with age. The purpose of 
these papillz, one series of which occurs in the anterior third, the other in the pos- 
terior, evidently was to prevent undue overlapping of the valves by presenting an 
obstacle to the entering ventral edge of the left valve. 
Of this species, I have before me no less than five hundred specimens, represent- 
ing twelve localities in the states of Minnesota, Wisconsin, Illinois, Kentucky and 
Tennessee. Considering its wide geographical range and abundance, it is remarka- 
bly constant in all its characters. That it is so in its outer form is clearly enough 
shown by the above measurements, taken from representative examples. They show 
further that the northwestern specimens are on an average about one-third larger 
than those from Tennessee. In all other respects however they are all practically 
identical. 
In 1890 (loc. cit.) I believed it probable that L. josephiana Jones, would prove 
distinct from L. fabulites, but it is now quite evident to me, as it also has become to 
Prof, Jones, that there is no ground whatever for any distinction between them. 
Compared with other species, the Upper Silurian L. hisingeri Schmidt, is not far 
removed, and the variety fabulina from Lake Winnipegosis very similar indeed. Still 
as pointed out by Prof. Jones there are a number of minor differences between them, 
and these will no doubt be added to when the later form is fully known. Another 
closely related form is the L. wiluiensis Schmidt, from the Upper Silurian of Russia. 
Its hinge line is shorter and the antero-ventral curve somewhat fuller, but in other 
respects, even to the rows of puncte along the ventral margin, the two species are 
much alike. L. linneyi Ulrich from the Upper Trenton of Kentucky is more obliquely 
produced posteriorly and has a shorter hinge line, a flatter ventral edge, distinct 
flanges, and better developed tubercle and muscle spot. 
