298 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



thin, thread-like, with closely packed pinnules. Regular interbrachials : 

 1, 2, 3, and others above, which gradually intermingle with the interambu- 

 lacrals. The first interbrachial of the anal side is somewhat the largest, and 

 is followed by three plates in the second row, which form an arch, and by 

 four pieces in the third and fourth rows. Ventral disk low, depressed-pyra- 

 midal, apparently surmounted by a subcentral anal tube ; the plates more 

 or less uniform, of about medium size, and somewhat convex. 



Horizon and LomlUy. — In a limestone layer, six inches in thickness, 

 above the base of the Black Slates, Bainbridge, Koss Co., 0., and at Canan- 

 daigua, N. Y., in rock of about the same age. 



Type in the Ohio State collection, Columbus. 



Remarks. — Prof J. M. Clarke of Albany had the kindness to send us 

 guUa-percha casts of the types of Melocriniis Clarkei Williams, which we 

 regard as identical with M. hainhridgensis, 



Melocrinus gracilis W. and Sp. (nov. spec). 

 Plate XXII, Fig. 5, 



A rather small species, of the type of Melocriniis {Ctenocrinus) stellaris 

 Roemer. Dorsal cup obpyramidal ; the radials and costals strongly curved 

 so as to form broad, very conspicuous longitudinal ridges with a small 

 tubercle at the centre of each plate, those of the axillaries being the longest 

 and sharpest. Interbrachial spaces depressed, giving to the section across 

 the second costals a sharply pentangular, somewhat stelliform outline. 



Basal cup low, broadly truncate at the bottom, its lower edges slightly 

 projecting beyond the column ; the upper angles turned abruptly upwards. 

 Radials and costals nearly equal in size, wider than long, but the curvature 

 makes them appear to be longer than wide. Distichals 2X10, rounded like 

 arm plates ; short, transversely arranged, those of the same ray separated by 

 one or two minute interdistichals, which rest within the bottom of a shallow 

 pit. The arm trunks bend outward, are heavy, and composed of two rows 

 of short pieces. The arrangement of the arms cannot be ascertained, as in 

 the single specimen the trunks are preserved only to the fourth plates, and 

 of the arms only fragments of a single one. Interbrachials numerous, 

 slightly decreasing in size upward ; arranged : 1, 2, 3, 3, -etc. They are 

 somewhat convex and ornamented with obscure radiating ridges, which con- 

 nect with the interambulacral plates. Ventral disk elevated, and, so far as 



