232 Twenty-fourth Report on the State Museum, 



the middle, so that the anterior portion of the valve forms a rounded 

 area which is often the most prominent part of the body, though in 

 some specimens the central ridge is equally prominent. 



Surface minutely granulose. Length about six-hundredths of an 

 inch, width about three-hundredths. 



This species differs from the B. oculifer in being destitute of the 

 prominent eye tubercle. 



Formation and locality. In the Hudson-river rocks at Jincinnati, 

 Ohio, from old collections. 



Beyrichia octjlifer n. sp. 

 Plate 8, figs. 9, 10. 

 Carapace small, seldom exceeding seven-hundredths of an inch in 

 length, by three to four-hundredths in the greatest breadth in the 

 largest specimens ; valves obliquely subreniform, broadest near the 

 anterior end, with a straight hinge line, which is a Ijttle shorter than 

 the greatest length of the valve ; anterior end projecting beyond the 

 hinge ; center moderately convex, with a proportionally broad, deep 

 channel just within f-he margin, extending all around it, except for a 

 short distance at the posterior extremity near the dorsal, margin. 

 The body of the valve is crossed obliquely by two deep furrows, 

 having their origin on the dorsal margin, the posterior one situated 

 a little more than one-third of the length of the valve from the 

 posterior extremity and extending fully two-thirds across it ; the 

 anterior furrow is situated just behind the anterior third of the length, 

 and in its lower portion is more strongly curved forward than the 

 other. Eye tubercle large, pedunculated, very prominent, and*^ spread- 

 ing at the top, its surface equal to about one-third the width of the 

 valve, and its height at the posterior margin equal to the breadth of 

 the top, while the anterior margin is but little elevated, giving an 

 obliquely sloping circular surface, with a denticulated border. This 

 surface, under a strong magnifier, is seen to be covered by fine eye- 

 like facets,* similar to those of the eyes of trilobites of the genus 

 Ill^nus. 



This species is very distinct from any other described, in the form 

 and strength of the transverse furrows, and especially in the great 

 prominence of the club-shaped eye tubercle. So far as can be ascer- 

 tained, it is the first species of this group of crustaceans in which 

 the eye facets have been detected. 



Formation and locality. In the Hudson-river shales at Cincin- 

 nati, Ohio. From Mr. C. B. Dyee, and also among old collections 

 from the same locality. 



* A feature first observed by Mr. Whitfield. 



