71 
posterior edges of the buckler; those of the I. Me- 
galops are not only much larger, but they are round, 
and very near the posterior border of the head. 
IsoreLus Srecops.* Green. Casts Nos. 26 and 27. 
Clypeo antice, caudaque postice attenuatis; cute | 
coreacea punctis minimis. 
The head of this species is nearly in the form of a 
spherical triangle; its anterior edge is vertically flat- 
tened all round, but does not produce a narrow raised 
rim, such as is described by Dr. Dekay, to belong to 
the Il. gigas. The eyes are prominent, and rather 
nearer the lateral edge of the buckler, than to its pos- 
terior border. The shell of the buckler forms a re- 
markable projection over the top of each oculiferous | 
tubercle, something like an eye-lid. Continuous 
with the edge of this cuticular projection, there is a 
curved linear depression, which terminates on both 
sides, at the edge of the buckler. This kind of 
suture, though remarkably developed in this species, 
is not peculiar to it, being more or less distinct in 
most of the Isoteli. The articulations of the abdo- 
men are lost; there can be little doubt, however, that 
they were eight in number. The tail is subtriangu- 
lar, and less in magnitude than the buckler. 
. This fossil is among the number of fine specimens 
in the cabinet of J. P. Wetherill. It is ina rolled or 
* From two Greek words, which signify ‘‘ covered eyes.”’ 
