174 Cincinnati Society of Natural History. 
gin of the right valve, four in the posterior third, and three or four 
in the anterior third. On the outer side of the test these are gen- 
erally represented by an equal number of small pits. The purpose 
of these two sets of papillae seems to have been to prevent undue 
overlapping of the valves, by presenting an obstacle to the enter- 
ing ventral edge of the left valve. 
Such pits at the ventral edge of the right or overlapping valve, 
(and I think we may safely assume that they always represent 
internal papillz,) are known to me in at least three other species, 
L. linneyi and L. tumidula, the two next described, and Z. dzma, 
White.* In the first of these there are two in the anterior half 
and one or two in the postericr, but in the other two species only 
one occurs on each side. 
It is possible that the Canadian species Z. josephana, Jones, is 
the same as L. fabulites, but as that species often, if not always, 
exhibits an anterior tubercle on the owfer side of the carapace, and 
since no pits nor papillz have as yet been detected on the ventral 
margin, it is reasonable to suppose that Prof. Jones’ species may 
prove distinct. 
Position and locality: In Tennessee the species is very abun- 
dant in Safford’s ‘‘ Glade limestone” at Lebanon, Lavergne and 
other localities. This limestone I regard as equivalent to the 
Birdseye of New York. The species occurs also in the ‘‘ Central 
limestone’ near Murfreesboro. In Kentucky, silicified valves are 
sometimes very abundant near the top of the Birdseye at High 
Bridge, VAt Dixons all> Beloit, Wis., Minneapolis, Minn., and 
other localities in the northwest, the species is a characteristic fos- 
sil of the lower portion of the series of limestones resting on the 
St. Peters sandstone. This horizon I regard as equivalent to the 
‘‘Glade”’ of Tennessee, and the Birdseye of Kentucky and New 
York. 
LEPERDITIA LINNEYI, Nl. Sp. 
Plate XT fies. 3 a—— 26: 
Right valve: Length, 10.45 mm_; height, 6.9 mm.: thickness, 2.25 mm. 
Size: Left “c 66 Biss) ff 66 es a ‘6 2.5 be 
6é ce ee 7.8 ee oe 4.95 te “e r.8 ce 
Carapace of medium size, oblique, produced and widest poste- 
riorly ; ventral edge rather strongly arched, rounding neatly into 
the anterior margin. Cardinal line straight, both the extremities 

*The two supposed perforations at the ventral edge of the same valve of 
the Russian Z. grandis, Schrenk, are doubtlessly of the same nature. 
