522 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
those of the intervening joints angular; the axial canal rather large and 
circular. | 
Horizon and Locality. — Niagara group, above the shales ; Lockport, N. Y. 
Types in the American Museum at New York. 
femarks. — P. speciosus, which was made by Hall the type of Saccocrinus, 
is the only known American Periechocrinus in which the second bifurcation 
takes place in the arms. 
Periechocrinus Whitfieldi (Hatt). 
Plate LI. Figs. 1, 2a, b, 3, 4. 
1863. <Actinocrinus Christyi— Hauu; Trans. Alb. Inst., Vol. IV., p. 196. (Abstr., p. 2), not Actinocrinus 
Christyt Shum., 1855. 
1868. <Actinocrinus Whitfieldi — Hau; 20th Rep. N. Y. State Cab. Nat. Hist. (Doc. Hdit.), p. 326. 
1863. Saccocrinus Christyi— MErx and WortHEN; Geol. Rep. Illinois, Vol. IIT., p. 347, Plate 5, Fig. 1. 
1870. Actinocrinus (Saccocrinus) Whitfeldi— Hatt; 20th Rep. N. Y. State Cab. Nat. Hist. (Revised 
Ed.), pp. 370 and 4:30. 
1877. Saccocrinus Christyi —S8. A. Mittrr; Catal. Amer. Paleoz. Foss., p. 90. 
1879. Saccocrinus Christyi— Hatt; 28th Rep. N. Y. State Cab. Nat. Hist. (Revised Ed.), p. 127, Plate 
18, Figs. 12-20. 
1881. Periechocrinus Christyi —W. and Sv.; Revision Paleocr., Part II., p. 182. 
1881, Saccocrinus Christyi —Watt; 11th Ann. Rep. Indiana, p. 254, Plate 12, Figs. 12-20, Plate 15, 
Figs. 3, 4. 
A moderately large species. Calyx subovate; the dorsal cup urn-shaped, 
its sides convex and but slightly spreading below the arm bases; the ventral 
disk low hemispherical, the plates thin and flat, the radial ridge proceeding 
from the middle of the radials to the arms rather obscure. Surface of plates 
finely granulose, the granules arranged in excentric lines, parallel to the 
margins of the plates. 
Basals large, more rapidly spreading than the succeeding plates. Radials 
and costals decreasing in size upwards; the radials nearly three times as 
large as the second costals, and longer than wide, the upper and lower faces 
much smaller than any of the others. Distichals two, of the size of the sec- 
ond costals, supporting two or three small palmars, which are succeeded by 
the arms, the structure of which is not known. Interbrachials: 1, 2, 2, 2, 
sometimes with a sixth row within the arm regions; the plates, as a rule, 
are longer than wide, and agree in size with adjoining brachials. Interdis- 
tichals 1, 2, 2; the lower one larger, resting between the first distichals. 
Anal interradius very wide ; the anal plate of equal width with the radials, 
but not quite as long; the three plates of the second row longer than wide; 
the middle plate the narrowest; the third row also consists of three plates, 
