NOTES ON PALEOZOIC CRUSTACEANS 9^ 



Jones and Woodward.^ The difference lies herein, that the speci- 

 men, which preserves with distinctness the structure of the 

 cephalic region, shows very clear evidence of an ocular node. 

 Drs Jones and Woodward, in the discussion of their proposed 

 genus E m m e 1 e z o e, have remarked on the valuation of this 

 feature as follows (p. 69). 



The presence of the ocular tubercle has an important signifi- 

 cance, showing that the animal must have had the organ equiva- 

 lent to the eye sufficiently developed to affect the external cover- 

 ing, whether it was adapted to clear vision or not. It is not only 

 a generic character distinguishing them from O e r a t i o c a r i s, 

 but probably an important family distinction. At all events the 

 oculate carapaces have to be remioved from C e r a t i o c a r i s . 



Generic distinctions among the Phyllocarida are not readily 

 determined, nor have thoee suggested proven altogether stable. 



The tenuity of these carapaces and abdominal parts has led in 

 several notable cases to the introduction of superfluous terms as 

 generic designations. Perhaps we should be inclined to lay less 

 emphasis than another on this external evidence of the eye-spot 

 on the carapace, but in deference to the judgment of the high 

 authorities cited, the term above used, Limnocaris, may 

 serve as an expression of this putative generic difference. 



Speoific oharacters. Carapace very large, each of the valves 

 horizontally sub-semiovate. Hinge line straight from posterior 

 extremity to near anterior, where it is slightly deflected to leave 

 place for a rostral plate. The anterior extremity is blunt, nar- 

 row, its margin being nearly straight for a short distance. The 

 carapace widens from the anterior end rather gradually with a 

 gently outward marginal curve, and attains its greatest width 

 near the middle of its length, where this width is more than one 

 half the length on the hinge. The posterior end has a width 

 somewhat more than one half the median width, and its margin 

 is gently incurved, forming a broad posteroventral and a small, 

 acute posterodorsal angle. The margin on the anterior ventral 

 and posterior curves bears a fine elevated cord. 



^British paleozoic phyllopoda, pt 1, Ceratiocaridae. Paleontogr. soc. 



1888. I M 1 



