764 THE CRINOIDEA CAMERATA OF NORTH AlIERICA, 



stri» vertically arranged, and all continued to the basals, where the corre- 

 sponding ones meet with those from adjoining radials at acute angles; the 

 striae in well preserved spechnens showing a rhombic arrangement. 



Basal cup rather flat, presenting a shallow basin ; the columnar attach- 

 ment very small. Radials a little longer than wide ; the lower faces a little 

 convex; facets shallow, occupying about one half the width of the plates. 

 Structure of the disk and arms unknown. 



Rovizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 



Type in the Museum of Comparative Zoology. 



Dichocrinus CinCtUS Miller and GuKLET. 

 Plate LXXV. Fig. 5, and PMe LXXVII. Figs. 4a, h, c. 



1890. Miller and Gokley; Joum. Cbciu. Soc. Nat. Hist., Vol. XHI., p. 21, Plate i, Figs. 10 to 13. 



A small and slender species. Calyx fusiform, widest across the middle 

 of the radials, whence it tapers both ways ; cross section circular ; suture 

 lines indistinct ; surface of plates highly ornamented. The radials are 

 covered with five or sis longitudinal ridges, which follow the median 

 portions of the plates to near the foot of the basals. The ridges do not 

 quite reach the top of the radials, and their upper ends are rather obscure ; 

 but toward the lower end, and especially upon the basals, they grow quite 

 prominent, and terminate in a sort of thickened collar around the column 

 facet, giving to the specimens an • appearance as if the inner part of the 

 base consisted of an independent set of plates. The longitudinal ridges 

 are faced laterally by horizontal ones, which traverse the interradial sutures, 

 and enter the margin of the adjoining plate. 



Basal cup obconical, rising to two fifths the height of the calyx, the 

 upper angles slightly bending inward ; radials somewhat projecting next to 

 the facet into a lip ; facets directed upward, not occupying more than one 

 third the width of the plates. Costals short, very closely united. Arms free 

 after the first bifurcation ; simple, slender, long, and uniserial throughout ; 

 joints convex, slightly cuneate, and very short; the two proximal ones 

 united by syzygy, with striated, apposed faces (Plate LXXYIL, Fig. ic). 

 Pinnules in close contact, and of moderate length and width. Anal plate 

 longer than the radials, and more inflected at the upper end. It supports 

 a number of small irregular plates, which form a small protuberance enclos- 

 ing the anus ; the latter opening out laterally. Ventral disk low-pyramidal ; 



