412 PROCEEDINGS OF THE ACADEMY OP 



Genus RHODOCRINTJS Miller, 1821. 



Rhodocrinus Halli, n. s. Plate iv., fig. 5 a-b. 



Body vasiform, one-third wider than high, composed of slightly convex and 

 plane pieces, connected by distinct depressed sutures. The lines of the rays 

 are prominent, while the interradial fields between them are nearly level, 

 giving the calyx a pentagonal figure at the summit of the second radials. 

 Columnar facet large, covering nearly the whole of the basal pieces, the angu- 

 lar points alone project beyond the column. Basal pieces five, short, lanceo- 

 late, crenulated and concave at their union with the column. Subradial 

 pieces five, convex, three are pentagonal, the summits of the other two are 

 truncated and hexagonal ; one truncated piece supports the anal field, the 

 other being the second to the left of the anal piece. A slight elevation rises at 

 the lower side of the subradials, runs to the centre of them, when it branches ; 

 a branch from the subradials on either side uniting at the centre of the first 

 radial piece. The first primary radials two, one septagonal, two hexagonal, 

 the second to the left of anal field being pentagonal ; they alternate with the 

 subradials, rising from the angular notch between them, and with the first 

 anal piece from a closed circle around the calyx. The second primary radials 

 are quite small when compared with those below ; they differ in size and are 

 all hexagonal. The third primary are axillary, pentagonal, less than the 

 second series ; they each support one brachial piece on either of their oblique 

 upper margins ; from this last piece appears to rise the free arms. Interra- 

 dials the first are large pentagonal, each supporting two smaller pieces ; these 

 again support three ; the fourth series appears to consist of four pieces. Our 

 specimen does not show the upper part of any interradial field perfectly. The 

 first anal piece is hexagonal ; it supports three pieces, the central one pentag- 

 onal, the other two hexagonal, these support five (?). Arms ten, column 

 round, perforation small, (obscure on our specimen,) it is nearly round, or 

 slightly pentelobate. 



Dimensions. 



Height of specimen '85-100 inch. 



Greatest diameter (specimen slightly crushed) 1-80-108 " 



Diameter of base -40-100 " 



Geological position and locality. Collected by Dr. J. Knapp, in the same 

 beds as specimens described in this paper under Nos. 43, 44 and 49. Named 

 in honor of James Hall, Esq., of Albany, N. Y. 



Genus MAGESTOCRINUS Owen & Shumard, 1848. 



Magestocrinus Knappii, n. s. Plate iv., fig. 6 a-b. 



Calyx subglobose, base broad, nearly fiat to the end of the second primary 

 radials, slightly depressed at the basal pieces. Base composed of three pieces, 

 nearly equal in size, together they present an oblong hexagonal disk. First 

 primary radials hexagonal, nearly equal in size, about as wide as high, upper 

 margins straight and parallel to the base of the pieces, the base a little wider 

 than the summit of the pieces. Second primary radials hexagonal, less than 

 the first radials, each surmounted by a short thick spine, the base of which 

 covers the surface of the piece. Third radials axillary, less than the second, 

 each surmounted by a spine like the second radials ; the spines on the differ- 

 ent third radials vary in size ; they taper more rapidly than the spines on the 

 second radials. Each third radial supports on its upper oblique upper mar- 

 gins two secondary radials, each of which is surmounted by a short obtuse 

 spine, more or less prominent ; two or three oblong non-spinous pieces are 

 supported by these, which reach to the free arms. Interradial pieces : the first 



[Dee. 



