766 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Dichocrinus delicatus W. and Sp. (nor. spec). 

 PUe LXXVII. Fig. 13. 



Of the type of D. Icevis, but smaller ; the calyx more elongate, its height 

 twice its width ; cross section circular; plates thin and apparently without 

 ornamentation ; suture lines indistinct. 



Basals occupying two fifths the height of the dorsal cup, the sides a little 

 convex. Radials fully twice as long as wide ; the lateral faces about parallel ; 

 the upper face nearly straight, not sloping at the sides ; the facet for the 

 reception of the brachials slightly indented, occupying less than one half the 

 width of the plates. Primary brachials two, short, of equal width ; the sec- 

 ond a little longer, its upper sides forming an obtuse angle, and giving off 

 two arras which remain simple throughout. Arms long, C3'lindrical, but little 

 tapering ; uniserial, composed of very short quadrangular joints ; their upper 

 and lower faces almost parallel ; the pinnules in rather close contact, long, 

 slender. Anal jDlate of equal length with the radials, the upper end narrower 

 than the lower. Ventral disk and anal opening not visible in the specimens. 



Horison and Locality. — Kinderhook group of Marshall Co., Iowa, and 

 Lower Burlington limestone of Burlington. 



Ti/pes in the collection of Wachsmuth and Springer. 



Remarks. — Dichocrinus delicatus made its appearance before D. Icevis, and 

 may be regarded in a phylogenetic sense as the earlier stage of that species, 

 as indicated by the arm structure ; the arm joints are quadrangular in the 

 several specimens found, while in that species they are cuneate and inter- 

 locking at the tips of the arms. Besides, this has invariably two arms to the 

 ray instead of four as in D. Icevis, and the specimens are generally smaller. 



Dichocrinus superstes w. and Sp. (noT. spec). 



Plate LXXYI. Fig. M. 



A small species of the type of D. cleUcatus. Dorsal cup obconical, higher 

 than wide, spreading more rapidly at the basal cup than from there upwards. 

 Cross section hexangular, owing to an angularity passing from the radial 

 facets and upper part of the anal j^late to the lower ends of the basals. 

 Plates without ornamentation, thick, and the sutures obscure, except the 

 interradial, which are somewhat grooved at the upper end. 



