1881.] NATURAL SCIENCES OF PHILADELPHIA. 299 



Basals united by anchylosis, without A'isible suture lines, and 

 forming a pentagon ; small, often barely extending beyond the 

 circumference of the column ; the median part strongly concave 

 or the entire base funnel-shaped ; central perforation or passage 

 for the columnar canal ver}^ large, pentalobate. 



Radials 3X5; the first large, hexagonal ; the second quad- 

 rangular, generall}^ with convex sides, narrower than either second 

 or third, but much wider than high. The third pentagonal, and 

 supporting at each side two secondar}' radials, which give off two 

 arms to each ra^'. In the majority of species, however, there are 

 two pairs of tertiary radials above the second order, or four arms 

 to the ray. The secondarj^ radials, and the tertiar}^ ones if these 

 are present, are almost as large as the second and third primaries. 

 The arms, on becoming free, bifurcate two or three times, and it 

 appears that they were constructed sometimes of a single series of 

 cuneiform pieces alternately arranged, but more gene rail}' of two 

 series of interlocking plates. Pinnules long, slender jointed. 



Interradials three or more — their number greater in species 

 with four arms than in those with two arms to the ray — generally 

 arranged in three series. The first interradial plate very large, the 

 largest plate in the calj^x ; subcircular to subovoid ; resting 

 between the upper sides of the first radials, against the sides of the 

 second and third, and between the lower sloping sides of the first 

 secondary radials. The second interradial series is composed of 

 one or two plates, smaller than the first. The third series consists 

 of two or three much smaller plates, sometimes with a fourth series 

 above. There are generally a few interaxillar}" plates between the 

 secondary radials. 



Vault composed of rather large plates, ornamented with coarse 

 granules or small irregular nodes. The apical dome plates well 

 defined, the radial pieces slightly tuberculous, and the entire 

 radial portions elevated ; the interradial regions depressed. Anal 

 aperture subcentral, evidentl}^ extended into a slender tube. 



Column unknown, its form however was circular, and it had an 

 unusuallj"^ large, pentalobate central canal. 



Geological Position^ etc — In the Upper Helderberg and lower 

 beds of the Hamilton group, Devon., and only found in America. 



1862. Dolatocrinus glyptus Hall. (Cacabocr. glyptus). 15th Rep. N. York St. Cab. 

 Nat. Hist., p. 140 ; Dolatocr. glyptus S. A. Miller, Cat. Pal. Foss., p. 72. 

 Hamilton gr. Genessee Co., N. Y. 



