PALEONTOLOGY. 417 



border, lacking that subquadrate form characteristic of those species. 

 The eyes are proportionally smaller, and situated near each other, and 

 also farther forward, as well as being somewhat 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 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 con- 

 tact. The head does not show evidence of having been margined by an 

 elevated 01 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. 

 microphthalmia 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 semi-circular form. The eye-tubercles are 

 also more nearly of the size of those of that species and similarly situ- 

 ated. 



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 character. 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, and parallel to the anterior and posterior margins 

 of the segments, instead of being irregularly disposed, as in all other 

 species described. No indication of the longitudinal rows of larger 

 pustules, marking the median line of the thoracic segments can be 

 traced. Caudal spine not observed. 



OSTRACODA. 



Genus LEPERDITIA Ronault. 



Leperditia alia. 



Plate I, fig. 27. 

 Cytherina alia (Con.) Vanuxem, Geol. Rept, 3d Dist. N. Y., 1843, p. 112, fig. 6. 

 Leperditia alta (Conrad) Jones, Ann. and Mag. Nat. Hist., vol. 17, 2d series, p. 88; 

 Hall, Pal. N. Y., vol. 3, p. 373; Meek, Pal. Ohio, vol. 1, p. 187, pi. 17, fig. 2. 



Valves of the carapace transversely sub-ovate, widest posterior to the middle 

 and narrowed in front, the proportional height and length being somewhat variable, 

 but are usually about as two and three. Hinge-line straight nearly two-thirds as 

 long as the entire valve, extremities salient. Anterior end of the valves narrowly 

 rounded and the posterior extremity broadly curved; basal-line curved but with a 



27 G. O. 



