4a0» PALAEONTOLOGY OF NEW-YORK. 



as Onchus deweyi*. The structure of this fossil, under a microscope, is 

 eminently crustacean ; and from our present knowledge of this, with 

 other fragments, spines, etc., it appears conclusive that we have several 

 species of the genus in our strata. 



The spines, either separated, or connected (as they are when perfect) 

 in a triple arrangement, have been termed Leptocheles by Prof. M'CoY ; 

 and subsequeiitly their true relations have been discovered. 



Genus Ceratiocaris ( M'Cot). 



" Carapace bivalved. The dorsal line simply angulated ( ? undivided) with 

 " a slight furrow beneath it on each side : sides semielliptical, much 

 " elongated from before backwards, very convex ; ventral margin 

 " gently convex, posterior end abruptly truncated obliquely. On each 

 " side, near the anterior end, considerably below the hinge-line, is an 

 " ocular (?) spot, sometimes raised and distinct, in sdme species flat. 

 " Surface marked with fine, obliquely longitudinal imbricated striaef ." 



Mr. Salter has given| a diagram of this fossil, " from perfect specimens found in 

 " Lanarkshire". The accompanyjng figure is copied from the one cited. 



Fig. 8. 



There are fir& articulations, besides the triple caudal spine. In our specimens, the relations 

 of the three spines differ somewhat from that represented in the figure, as will be seen by 

 reference to the plates. 



• Page 320, Plate Ixxi, fig. 1. 



t British Palaeozoic Fogailg, p. 186. 



i Quarterly Journal of the Geological Society of London, Vol. xil, p. 88. 



