326 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
and a number of small plates in the ventral disk. Disk depressed-hemi- 
spheric; the interambulaeral spaces nearly on a level with the ambulacra; 
all the plates slightly convex. Anal tube large at the base, and almost 
central. 
Horizon and Locality. Hamilton group; Davenport, Iowa. 
Types in the Museum of the Davenport Academy of Sciences. 
Remarks. — The small specimen which Barris described as variety “ Tira- 
tus,’ is in our opinion not sufficiently distinct for separation, and, it seems to 
us, the differences given are readily explained by individual growth. 
Stereocrinus Barrisi W. and Sp. (nov. spec.) 
Plate XXV. Figs. 9a, b. 
Syn. Stereocrinus triangulatus Barris (in part). 
Of medium size. Calyx more than once and a half as wide as high, 
flattened to the top of the radials, and slightly depressed at the basals; the 
sides from the middle of the costals rising vertically; lobed at the arm 
bases. Ventral disk short, slightly tumid, the interambulacral spaces deeply 
depressed so that the ambulacral regions are conspicuously elevated. Plates 
of the dorsal cup covered by similar sets of triangles as in the preceding 
species, but the ridges forming them more prominent, and there is a node in 
the centre of each plate; suture lines difficult to see. The column is sur- 
rounded by a strong circular ridge. 
Basal disk projecting beyond the column. Radials and costals nearly 
equal in size, the former hexagonal, the others heptagonal. Distichals three 
in the calyx; the first a third the size of the costals; the second and third 
extremely short, the latter facing laterally. First interbrachial very large, 
the two of the second row much smaller. Ambulacral openings large, elon- 
gate. Respiratory pores four to each interradius, and two above the inter- 
distichal spaces. Orals rather large, slightly tumid, pushed to the anterior ; 
the posterior one resting against the base of the anal tube, which is almost 
central. The plates covering the food grooves small and tuberculiform ; the 
interambulacral ones somewhat larger and almost flat. Column small, round ; 
the axial canal large and pentalobate. 
Horizon and Locality. — Hamilton group ; Alpena, Mich. 
Types in the Museum of the Davenport Academy of Sciences, and in the 
collection of Wachsmuth and Springer. 
Remarks, — This species has close affinities with the preceding one, and 
