844 THE AMERICAN NA TURALIST. [Vol. XXXVII. 



The eyes, therefore, of Cephalaspis, like those of Tremataspis 

 and Bothriolepis were imbedded between two layers of the der- 

 mal armor, and in this respect agree with the condition which 

 prevails in both the median and the lateral eyes of Limulus (Fig. 

 8 A). 



Two depressions lie just in front of the orbits (the so-called 

 ant-orbital fossa' [a./.). They are separated by a median crest, 



the summit of which is perforated by a narrow slit which leads 

 into the interior of the beach 



On the inner surface of the shield, near the lateral margins. 



