OK THE GAMPSOKTCHIDJE. 133 



scended from Acantliotclsoii, which is thus a truly synthetic form, standing in an ancestral relation 

 to all the Thoracostraca, while it also suggests that the sessile-eyed and stalked-eyed Crustacea 

 may have had a common parentage. 



Explanation of Plate III.' 



Fig. 1. Palcsocaris typua, M. <fe W. restored, enlarged four times. (The front of the head is partly conjectural 

 and though stalked eyes probably existed, uo attempt has been made to restore them.) 



Fig. 2. Pala-ocari'i lypus, seven thoracic segments, showing the disposition of the endopodites, x? (Lacoe's 4046). 



Fig. 3. Palwocaris lypus, doTaal view of one side of three thoracic segments, showing the basal joints of the en- 

 dopodites {endop), and exopodites (ejojj), enlarged. 



Fig. 4. FalcBocaris typm, telson and last pair of uropoda. Xf. 



* All the figures on this plate drawn by Dr. J. S. Kingsley. 



