4 WW 



KlI'olM <•!■ IM:(HiKi;ss. c. K. IJEKCllEK. 



near the summit of tliis tubercle as in the ooelli of Euryi^- 

 fcrifs, etc. Tlie fact that facets cannot be discerned is no 

 criterion of tlieir absence in the animal, for numerous trilo- 

 bites and Euryjjterus have as yet revealed no evidence of 

 the compcnind character of their eyes, and on the other 

 hand many species have large and distinct facets. It has 

 also been noticed by Professor McCoy that this spot on the 

 carapace is darker in the fossil than the general surface of 

 the carapace, indicating the presence of pigment in the 

 animal at this point. In the specimens of Elymocaris 

 siliqua, Tropidocaris hicarlnata and T. interrupta of the 

 present paper this character is well marked. 



« Explanation of Fig- 1. 



1. Anterior margin. 



VC^^vve 





2. Furrow Imiiting the 



cephalic region. 



3. Lower or ventral mar- 



gin of valve. 



4. Dorsal-line or hinge. 



5. Posterior margin. 



6. Articulating surface of 



somite. 



It 7. Fimbria or setse. 



8. Crenulated inner mar- 



gin of spine for the 

 attachment of setae. 



9. Caudal plate. 



10. Abdominal segments. 



11. Thoracic portion of the 



valve extending to 

 the furrow limiting 

 the cephalic area. 



12. Longitudinal ridge. 



13. Nodes on the thoracic 



area. 



14. Cephalic region. 



15. Nodes and elevations. 



16. Ej^e tubercles and op- 



tic spots. 



