CALYPTOCEINID^. 345 



Basal concavity a little wider than the column, and rather deep^ the basal 

 plates occupying almost its whole width. Kadials curving abruptly inward 

 at the lower end, forming a sharp edge at the bottom of the dorsal cup ; the 

 exposed upper part wider than long, and nearly as large as both costals to- 

 gether. First costals once and a half as wide as long ; the second a little 

 wider and pentangular. First distichals almost as large as the costals, the 

 second one third smaller, and the arm-bearing palmars about half the size of 

 the second distichals and pentangular. First interbrachial large, subcircular 

 in outline though actually decagonal ; it meets the two succeeding plates, 

 which are as long as the first, and near the lower end almost as wide ; the 

 upper parts tapering rapidly to a rather sharp point, which rises to the height 

 of the fourth arm pieces. Interdistichal narrower and shorter than the two 

 upper interbrachials ; the lower end angular and barely touching the upper 

 angle of the adjoining costal -, the projecting upper end narrow and truncate. 

 Compartments for the reception of the arms deep ; the partition walls thin 

 throughout, their width at the lower end half that of the arms, the outer faces 

 flat. The summit closed by a small rosette of about eight pieces without 

 additional plates. Arms very gradually tapering, the outer face slightly 

 .convex ; they are composed of moderately short pieces, which interlock 

 from the fourth plate. With the exception of the partitions nothing is 

 known of the construction of the disk. Column round, the nodal joints 

 high and cylindrical, the younger joints a little narrower; axial canal 

 pentalobate. 



Horizon and Locality. — Niagara group \ Waldron and Hartsville, Ind. 



Tyjpes in the American Museum of Natural History at New York. 



Remarhs. — This species has such close affinities with E. crassus that it 

 might be taken for its younger stage ; but on close inspection it will be ob- 

 served that the specimens have all the characteristics of an adult form. The 

 arms not only are biserial, but their plates are almost transversely arranged. 

 Moreover, the arms are placed deeply in between the projecting upper ends 

 of the interbrachials and interdistichals ; only in young specimens the tips 

 are almost on a level with the distal faces of the arm-bearing palmars. It 

 differs from U. crassus in its much smaller size, being only from 12 to 22 

 mm. in length by from 10 to 15 mm. in width, in the more evenly ovate 

 form of the crown, in not being truncated at the lower end, and in having 

 much shorter costals, and proportionally larger and pentangular arm-bearing 

 palmars. 



44 



