MELOCRINID^. 323 



Dolatocrinus speciosus (Hall). 

 Plate XXY. Figs. 4a, K 



1863. Cacahocrinus speciosus — Hall; 15tli Rep. N. Y. State Cab. Nat. Hist., p. 137. 

 1881. Dolatocrinus speciosus — W. and Sp. ; Revision Palseocr., p. 126. 



Of the type of D. major, but smaller ; the dorsal cup proportionally 

 higher, and provided with a somewhat deeper basal pit; the radials instead 

 of being stretched out horizontally, gradually slope toward the basal con- 

 cavity, without actually forming a part of it. It has but two distichals, and 

 two arms to the ray instead of four ; arranged in pairs with wide interspaces. 

 Cross-section below the arm regions subpentangular. Plates apparently 

 without ornamentation, their surfaces slightly convex; the median line of 

 the plates following the rays gradually rising into a keel-like projection or 

 carina, which passes up to the bases of the arms. This carina is higher upon 

 the radials and costals, and thickened at the middle of each plate, where it 

 is formed into a conspicuous elongate node ; the node of the first costals 

 more prominent than the others. 



Basals small, forming a shallow inverted basin, which is completely filled 

 by the column. Eadials larger than the costals, and about as wide as long. 

 The first costal narrower and shorter than the second, and quadrangular ; 

 the second obtusely angular above. Distichals 2 X 10, comparatively large ; 

 followed by a lunate arm plate. Arm openings two to the ray, directed 

 obhquely upwards, and those of the same ray packed closely together. First 

 interbrachial almost as wide as long, with an obtuse lower angle, and its 

 upper face broadly truncated ; the second about half the size of the first, its 

 lateral faces parallel. The latter supports three plates, two upon its sloping 

 lateral sides, and one upon the truncated upper face, which are followed by 

 a row of interambulacral pieces. The interdistichal spaces contain tw^o 

 plates. Ventral disk slightly convex, each side containing four interambu- 

 lacral plates, two of them larger and cuneate, touching the orals, the tw^o 

 smaller ones abutting against the secondary radial dome plates. The 

 posterior oral is deeply wedged in between the four others, and considerably 

 shorter. Anus almost central. 



Horizon and Locality. — Upper Helderberg group ; Western New York. 



The specimen figured is from the collection of Wachsmuth and Springer. 



