BATOCRINID^. 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. clepressus, 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 (Bakris). 

 Plate XLIX. Figs. 5a, b. 



1878. BiRRis ; Proceed. D.ivenp. Acad. Nat. Sci., Vol. II., p. 285, Plate 11, Kg. i. 

 1885. Bakris ; ibid., Vol. IV., p. 99, Plate 1, Pig. 8 and Plate 2, Pig. 2. 

 ISSl. W. aud Sp. ; Revision Palajocr., Part II., p. 138. 



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. Eadials and 

 costals increasing in width upwards; the radials longer than wide; the 

 costals wider than long. 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 3 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 larse. 



Horizon and Zoca%. — Hamilton group; Davenport, Iowa, and Alpena, 

 Mich. 



T//pes in the Museum of the Davenport Academy of Natural Sciences. 



