70 



rowness of the middle abdominal lobe, clearly distin- 

 guish it from either of Dr. Dekay's species. 



ISOTELUS MEGALOPS.* Green. Cast No. 25. 



Clypeo antice subrotundato, postice arcuato; oculis 

 magnis, rotundis, eminentissimis; caucla suborbicu- 

 lari, limbo latoj articulis abdominis octo. 



The buckler in its contour resembles very much 

 the head of the I. gigasj it is, however, rather more 

 rounded before, and arcuated behind. The oculi- 

 ferous tubercles, are very peculiar, being very large, 

 round, and exceedingly prominent. They have a 

 good deal the appearance of solid hemispheres 

 placed on the forehead of the animal. They are ex- 

 actly on a line with the two abdominal furrows. The 

 abdomen is composed of eight distinct articulations; 

 the middle lobe is rather larger than the lateral 

 lobes. The tail is suborbicular, convex, and rather 

 less than the head. Length nearly five inches. 

 Breadth almost three inches. 



This magnificent Isotelus was obtained near Tren- 

 ton falls, in New York, by P. A. Browne, Esq., and 

 now forms a part of his fine collection of fossils, in 

 this city. It occurs in black transition limestone. 

 It differs essentially from the I. gigas of Dekay, in 

 the magnitude, collocation, and contour of the eyes. 

 Those of the I. gigas are oblong and lunate, and 

 nearly half the distance between the anterior and the 



* From the Greek for " great eyes." 



