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. 



ISOTELUS STEGOPS.* 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 I. 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 in a rolled or 



* From two Greek words, which signify " covered eyes." 



