526 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
est width about one fourth its height; succeeding plates in rows of two, the 
upper ones small and irregularly arranged. Anal interradius wide, de- 
pressed between the arm bases, and forming at the ventral surface a rounded 
ridge, which connects with the anus; the plates very numerous and irregu- 
larly arranged. Interdistichals generally 1, 2,2. Ventral disk low-convex, 
the imterambulacral spaces depressed, the plates nearly flat. The food 
grooves in the cast are delineated by prominent ridges, which bifurcate half 
way out to the arms, and again close to the arm bases, giving off in the 
calyx four arms to the ray. 
Horizon and Locality. — Upper part of Niagara group, near Chicago, Ills. 
Ltemarks. — This species was regarded by Hall as a synonym of Periecho- 
cerinus Whitfeldi, but we agree with Miller that the two forms are distinct. 
The plates of P.Whitjieldi are flat and finely ornamented, those of P. anf elix 
convex and without ornamentation; the radials of the former possess promi- 
nent ridges, which are wanting in the other. We disagree with Miller, 
however, as to his “ Saccocrinus’’ Egan, which we take to be identical with 
P. infehix. 
Periechocrinus urniformis (8. A. Mitizr). 
| Plate L. Figs. da, b. 
1881. Saccocrinus urniformis —S. A. MittER; Journ. Cincin. Soc. Nat. Hist., Vol. IV., p. 170, Plate 4, 
Figs. 2, 2a. 
1885. Periechocrinus urniformis (?) —W. and Sr.; Revision Palxocr., Part IIT., p. 106. 
Syn. Saccocrinus pyriformis —S. A. Mintwr; 1882, Journ. Cincin. Soc. Nat. Hist., Vol. Vispa ps Olle 
Plate 3, Fig. 3. 
Syn. Periechocrinus pyriformis (?) —W. and Sp.; Revision Paleocr., Part IIT., p. 106. 
Only known from internal casts. Calyx large, ovoid; greatest width 
across the arm bases, which are somewhat projecting; plates gradually 
decreasing in width upwards. 
Basals small, forming a rather low cup. Radials and costals nearly of 
equal size; their width across the middle equal to their height; the upper 
and lower faces less constricted than in the preceding species. Distichals 
two, the first one fourth, and the second as much as one half, smaller than 
the costal axillaries. Palmars two, small. Interbrachial and interdistichal 
areas on a level with surrounding brachials, except close to the arm bases, 
where they form rather wide, well marked depressions, which are continued 
upon the tegmen. First interbrachial of about the same size as the first costal, 
but pentangular in place of hexangular; succeeded by six to seven rows of 
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