226 Twenty-fourth Report on the State Museum. • 



We may also suggest another explanation by supposing that the 

 adhering portion with the appendage are the base and column of an 

 unknown crinoid, the discovery of which may set at rest the question 

 concerning its nature. The remarkable striated attached surface 

 without extending fibres or rootlets, and the regular arrangement of 

 the plates upon the other side is so different from ordinary known 

 crinoidal bases as almost to preclude such an idea. 



Albany, Septemher^ 1871. 



Genus— LEPTOBULUS nov. gen. 

 AeTTToC, minutiis and obolus. 



Shell semiphosphatic, fragile, minute, more or less elliptical ovate 

 or subcircular, with moderately (or sometimes more extremely) con- 

 vex valves, which are concentrically marked on the exterior surface. 

 Ventral valve with a distinct area and pedicel groove ; interior with 

 an elevated subquadrate muscular area. Dorsal valve a little thick- 

 ened on the cardinal margin, with slightly elevated trifid muscular 

 impressions. 



There are, in the Utica slate of New York, and in the same hori- 

 zon in Iowa, and in the shales of the Hudson-river group at and near 

 Cincinnati, numerous minute, apparently phosphatic shells which 

 have usually been referred to Lingula, but without a knowledge of 

 their interior structure. The external form is so similar in all of 

 them that specific discrimination is often scarcely practicable. 



Among the specimens received from Mr. C. B. Dyer, are some 

 individuals which show the interior characters in a pretty satisfactory 

 manner. For these forms I propose the generic name Leptobolus. 



/ Leptobolus lepis n. sp. 



Plate 7, figs. 19, 20. 



Shell minute, ovate, or broadly elliptical in outline, about three- 

 fifths as wide as long, and seldom exceeding seven-hundredths of an 

 inch in length ; moderately convex, the greatest convexity being 

 about one-third of the length from the beak; ventral area thickened ^^ 

 pedicel groove strongly defined ; muscular impression broad, extend- 

 ing more than one-third the length of the valve ; muscular ridges of 

 the dorsal valve strongly marked, the central one extending two- 

 thirds the length of the shell, the lateral ones diverging from each 

 other at an angle of about forty -five degrees, and extending nearly to 

 the middle of the valve; extremities bifid. 



Surface of valves concentrically marked by fine lines of growth. 



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

 nati, Ohio. From the collection of Mr. C. B. Dyer. 



