516 Contributions to Invertebrate Palaeontology. 



shields and one body of a species of Eurypteriis, which is so dis- 

 tinctly different from any of those described, that it seems necessary 

 to class it as a separate species. The differences, so far as seen on 

 the parts preserved, consist in the form of the cephalic plate, in the 

 size and position of the eye-tubercles, and in the proportions of the 

 body as compared with the known forms. There are undoubtedly 

 other and more important differences in the appendages, but as 

 these are not preserved on any of the individuals examined, com- 

 parison is impossible. 



The cephalic shield is proportionally broader than that of E. 

 remipes or JE. lacustris, and is more regularly rounded or arched 

 on the anterior border, lacking that subquadrate form characteristic 

 of those species. The eyes are proportionally smaller, and situated 

 nearer each other, and also farther forward, as well as being some- 

 what more oblique to the longitudinal axis of the body. The minute 

 ocular points are somewhat larger than in E. remipes, are situated 

 close together, and are nearly opposite the posterior end of the real 

 e^^e-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 evidence 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 properl}^ 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. niicrophthalmus Hall (Pal. N. Y., vol. iii, p. 407,* pi. 

 80 A, fig. 7), from the Tentaculite limestone near Cazenovia, N. Y., 

 than of any other described species; it differs, however, in being 

 proportionately much shorter, which gives it a more semicircular 

 form. The eye-tubercles are also more nearly of the size of those 

 of that species and similarly situated. 



The thorax closely resembles that of E. remipes in its general 

 form, but the lower three or four segments are proportionally 

 shorter, giving the posterior extremity a much more compact char- 

 acter. The principal distinction between the two species, as shown 

 by the thorax, exists in a difference of the ornamentation of the 

 surface, as seen on the specimen used. This consists in the minute 

 spine-like pustules or pointed granules, marking the surface of the 

 crust, being arranged in irregular transverse lines across the body, 



