BATOCEINID^. 463 



Dorycrinus missouriensis (Shumard). 

 PMe XLIII. Pig. 6, and Plate XLY. Figs. 13a, h, c, and IJj.. 



1855. Actimeriims missouriensis — Shumabd ; Geol. Surv. of Missouri by Swallow, Part II., p. 190, Plate 



A, rigs. 4a, b, e. 

 1873. Dorycrimis missouriensis — Meek and Wokthen; Geol. Rep. Illinois, Tol. V,, p. 380. 

 1881. Dori/crinus missouriensis — "W. and Sp. ; Revision PaliEOcr., Part II., p. 179 (Proceed. Acad. Nat. 

 Soi. Phila., p. 353). 

 Syn. Actinocrinus desideraius Hall; 1861, Prelim. Descr. of New Palseoz. Foss., p. 2, and Boston 



Journ. of Nat. Hist., p. 353. 

 Syn. Dorycrinus desideratus — Meek and Wokthen ; Geol. Rep. Illinois, Vol. V., p. 380. 



A variable species, remarkable for the extravagant development of its 

 basal plates. Besides it differs from other species of this genus in the com- 

 paratively greater height of the dorsal cup, and the abrupt spreading of the 

 distichals and palmars, which stand almost at right angles to the radials and 

 costals. Calyx a little longer than wide ; the ventral disk from one fifth to 

 one fourth shorter than the dorsal cup. Plates thick, from almost flat to 

 strongly nodose, the nodes upon the radials transverse and most conspicuous. 



Base extremely large and heavy, spreading abruptly outward ; its dia- 

 meter in extreme cases equaling the width of the dorsal cup at the arm 

 regions, and reaching a depth as much as 15mm. ; interbasal sutures gener- 

 ally grooved and frequently notched. Radials about as long as wide ; the 

 sides nearly parallel ; subquadrangular in outline ; the sloping upper faces 

 very short ; the upper face concave. Costals very small, both together not 

 more than half the size of the radials ; their surfaces almost flat ; the firf;t 

 quadrangular, twice as wide as long ; the second one no longer but some- 

 what wider, and pentangular. The posterior rays have but one distichal, 

 which is quite small and axillary, and gives off from each side a single 

 palmar. The antero-lateral rays have two distichals, of which the second is 

 twice as long as the first ; the anterior ray generally has two distichals to 

 the left and one to the right, followed by palmars; but this ray also occa- 

 sionally has no palmar.?, and two distichals in both divisions. The arm- 

 bearing plates, whether distichals or palmars, are twice as long as the 

 preceding plate. The arms normally consist of fifteen pairs, arranged 

 in groups of 4, 2, and 3, with wide and deep inter.spaces between the 

 rays; they are short, rather stout for the genus, and bifurcate on a small 

 trigonal axillary, which occupies the same facet with the proximal arm 

 plates. Arm joints of medium size, and each fourth piece is produced 



