SILURIAN FAUNAS. 259 
ARTHROPODA. 
OSTRACODA. 
LEPERDITIA ALTA (Con). 
See, also, p. 265, pl. XXIV. 
In some beds of the Rondout formation there are numerous crushed 
specimens of a species of Leperditia, which, so far as can be deter- 
mined, possess the characters of L. alta, the species which is so abun- 
dant in the Manlius limestone, or of L. altoides, from the base of the 
Decker Ferry formation. 
LEPERDITIA ELONGATA DN. sp. 
Plate XXIIL., Fig. 13. 
Description.—Carapace large, obliquely subreniform, posterior ex- 
tremity the highest. Dorsal margin straight, two-thirds of the total 
length of the valves, its extremities obtusely angular. Anterior 
margin obliquely truncate from the hinge-line, sharply rounded in 
front into the broadly-convex ventral margin, which, in turn, curves 
regularly into the nearly semi-circular posterior margin. Hye 
tubercle distinct, situated a little above the middle of the antero- 
dorsal quarter of the valves. Both anteriorly and posteriorly the 
margin is slightly flattened in a rather indistinct marginal border, 
extending from the extremities of the hinge-line to the middle of the 
valve. Surface smooth. 
The dimensions of an average specimen are: length, 12 mm.; 
height, 6.5 mm.; convexity of one valve, 2.5 mm. 
Remarks.—Vhis species resembles L. alta, but is larger and more 
elongate. 
