280 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Basals five, forming an acute-angled pentagon. Radials large, wider 
than long; lunate. Costals two; the first quadrangular; the second much 
larger, almost as large as the radials. Distichals 2 X 10 in the calyx, the 
others free arm plates. Arms ten, simple, uniserial, rather stout; pinnules 
strong. Interbrachials: 1, 2, 1; the first very large, rising to the top of the 
first costals. Anal area wider, containing three plates in the second and 
third rows, and smaller ones above. Anus excentric, represented by a simple 
opening, which faces laterally. Ventral disk low, the orals very large, occu- 
pying in S. capitulum fully three fourths of the whole surface. Column 
round. 
Distriiution.— Hitherto found only in the Upper Silurian of Gotland, 
Sweden, but we now refer to this genus Walcott’s Glyptocrinus argutus from 
the Trenton limestone of New York, with some doubt. 
Remarks. — Angelin’s descriptions and figures are so confusing that no 
uniform generic characters can be deduced therefrom, unless some are elimi- 
nated. Taking the first species S. capitulum, Iconogr. Plate XVII., Figs. 
5-5g, and the first figures of his second species 8S. laevis, ibid., Plate XV., 
Fig. 20, we have the type indicated by the above descriptions; but Plate 
XXVIIL., Figs. 7a, b, figured also as S. laevis, is clearly a Desmidocrinus, and 
the specimen represented on Plate XX XII., Figs. 5 and 3a, is probably incor- 
rectly figured, either as to the anal side or the arms. Plate XIX., Fig. 6, 
figured as S. ovalis, is a totally different thing, and probably belongs to the 
Rhodocrinide. Plate XXI., Figs. 6, 7, described by Angelin as Harmocrinus, 
and considered by us (Revision, II., p. 99) as belonging to Stedidiocrinus, has 
very possibly a dicyclic base, and strongly resembles Thysanocrinus. We have 
not the material to settle these questions, but by restricting the genus to the 
above mentioned forms, we have something tangible. The genus, as thus 
defined, differs widely from any other of this group, especially in the struc- 
ture of the disk, which is quite remarkable. The quadrangular first costal 
distinguishes it from the associated genera with five basals. 
(?) Stelidiocrinus argutus (Watcor7). 
Plate XXIV. Fig. 6. 
1883. Glyptocrinus argutus —Watcorr; 35th Rep. N. Y. State Mus. Nat. Hist., Plate 17, Fig. 9. 
1885. (2) Stelidiocrinus argutus —W. and Sr.; Revision Paleocr., Part IT., p. 102. 
Calyx small, somewhat pentangular; the interradial spaces depressed. 
Basals five, rather large. Radials subquadrangular, the upper faces moder- 
