BATOCRINIDZ. 541 
Remarks. —We had for comparison a number of specimens from the 
American Museum at New York, some of which Prof. Hall had labeled 
M. depressus, others M. ontario. These specimens, in our opinion, differ only 
in the greater or less depression of the calyx from outside pressure, and 
in the greater convexity of their secondary radial dome plates, which in some 
specimens are strongly tuberculous, in others almost perfectly flat. 
Megistocrinus nodosus (Barris). 
Plate XLIX. Figs. 5a, b. 
1878. Barris; Proceed. Davenp. Acad. Nat. Sci., Vol. IL, p. 285, Plate 11, Fig, 4, 
1885. Barris; ibid., Vol. LV., p. 99, Plate 1, Fig. 8 and Plate 2, Fig. 2. 
1881. W. and Sp.; Revision Palwocr., Part II., p. 188. 
A large species. Dorsal cup broadly urn-shaped, the truncated part 
embracing basals, radials, and first anal plate, which are in about the same 
plane ; the sides of the cup, which rise from the lower end of the first costals, 
slightly convex, expanding near the arm bases. Plates without ornamenta- 
tion; but the costals and the interbrachials of the two proximal rows are 
somewhat nodose, while the radials are slightly convex, and the distichals 
and upper interbrachials almost flat. 
Basal disk but very little projecting beyond the column, the column facet 
excavated and surrounded by a well defined circular rim. Radials and 
costals increasing in width upwards; the radials longer than wide; the 
costals wider than lone, The higher orders of brachials arranged as in the 
preceding species. Arms sixteen from the calyx; long, slender, bifurcating, 
and composed of a double series of interlocking pieces. First interbrachial 
as large as the first costals; followed by three or four rows of two plates 
each. First anal plate succeeded by 3, 4, 4, and 8 plates. Interdis- 
tichals two to three. ‘Tegmen highly convex, somewhat inflated posteriorly, 
the interradial and interaxillary spaces deeply grooved from half way down 
to the arm regions; the posterior groove broadest and deepest; the surface 
paved by numerous irregular pieces, among which the orals are larger, 
subspinous, and not in contact; the radial dome plates strongly nodose. 
Anus subcentral. Column large. 
Horizon and Locality. — Hamilton group; Davenport, Iowa, and Alpena, 
Mich. 
Types in the Museum of the Davenport Academy of Natural Sciences. 
