628 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
upper ones together, the latter meeting the mterambulacral pieces. Inter- 
brachials apparently three. Ventral disk rather depressed near the outer 
margin; the central portions gradually rising to a good-sized anal tube, 
composed of moderately large, convex plates similar to those forming the 
' tegmen. 
Lorizon and Locality. — Niagara group; Yellow Springs, O., and St. Paul, 
Shelby Co., Ind. 
Ltemarks.— This species departs from the others in having a large anal 
tube, a character which in other groups has been regarded of generic im- 
portance, and we should propose for it a new genus if we were better 
informed as to the anal structure of the other species. 
Periechocrinus tennesseensis (Hatz). 
IAG SOR TU ESE 
1850. Saccoerinus tennesseensis —'TrRoost MS. | 
1875. Saccocrinus tennesseensis —Hatu; Geol. Rep. Ohio, Paleont., Vol. II., p. 125, Plate 6, Fig. 10. 
Syn. Saccocrinus speciosus — RormER (not Hat); Silur. Fauna des Westl. Tenn., p. 42, Plate 8, 
Figs. 3a, 6, ¢. 
Of the type of P. speciosus Hall, but the third division of each ray takes 
place in the calyx and not in the arms; and it has twenty primary arms in 
place of ten. Dorsal cup elongate obconical, one fourth higher than wide, 
slightly inflated at two thirds its height. Arm bases conspicuously projecting, 
deeply depressed between the rays and their main divisions; the depressions 
of the anal side widest and deepest. Surface of plates smooth, with a faint 
longitudinal elevation along the radial series, which at the top of the dorsal 
cup widens to the full width of the arms. 
Basals forming a somewhat conical cup. Radials much larger than the 
costals; the latter considerably narrower, and but little longer than wide. 
Distichals two, half the size of the preceding axillary, as wide as high. Pal- 
mars still:smaller, rounded like arm plates. Arms thin, cylindrical, arranged 
in pairs, biserial from their origin. Interbrachial areas composed of five or 
six rows; the plates arranged as in the preceding species, including those of 
the anal side. Ventral disk constructed of a number of polygonal plates 
without definite arrangement. Anus subcentral. 
fTorizon and Locality. — Niagara group; Decatur and Perry Cos., Tenn., 
and Yellow Springs, O. 
fiemarks. — The type specimen, collected by Dr. Troost, came from De- 
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