1U(! Xetv >Specic\s of Fo.y.'^i/s fro/ii Ohio. 



mimbei's densely packed together, but having the shelly sub- 

 stiinee entirely removed. 



ARTICULA^TA. 



Eiirypterus Eriensis, n. ,sp. 



ral. O., Vol. Ill, Plate 1, Figs. 81, ;j3. 



Among the fossils from the Hydraxilie limestones of Bcneh 

 I'oint, Put-in-Buy Island, Lake Erie, there are sevei'al detached 

 cephalic shields and one body of a sjiecies of Earypterns, which 

 is so distinctly different from any of those described, that it 

 seems necessary to class it as a separate species. The dilferences, 

 so far as seen on the i)arts preserved, consist, in the form of the 

 cephalic plate, in the size and position of the eye-tnbercles, and 

 in the proportions of the body as compared with the known 

 forms. There are undonbtedly other and more important dif- 

 ferences in the api)endages, but as these are not preserved on any 

 of the individuals examined, comparison is impossible. 



The cephalic shield is proportionally broader than that of 

 E. remijjes or E. lacustris, and is more regularly rounded or 

 arched on the anterior border, lacking that subquadrate form 

 characteristic of those species. The eyes are jjroportionally 

 smaller, and situated nearer each other, and also farther forward, 

 as well as being somewhat more oblique to the longitudinal a.xis 

 of the body. The minute ocular points are somewhat larger 

 than in E. reniipes, are situated close together, and are nearly 

 opposite the posterior end of the real eye tubercles ; they consist 

 of a pair of distinctly elevated rings surrounding rather deep, 

 although minute, central depressions ; the inner margins of the 

 rings being almost in contact. The head does not show evi- 

 dence of having been margined by an elevated or thickened rim, 

 as in those species, but as the specimens are rather impressions 

 of the inner surface of the external crust than actual external 

 surfaces (being more properly internal casts, the substance of 

 the carapace having been entirely removed), this feature may 

 not be properly shown. The head-plate more closely resembles 

 that of E. microjjMhalmus, Hall (Pal. N. Y., Vol. Ill, p. 407,* 

 pi. 80 A, fig. 7), from the Tentaculite limestone near Oazenovia, 

 N, Y,, than of any other described species ; it differs, however. 



