batocrinidjE. 527 



two plates each. Tnterdisticbab, 1, 2, 2 ; the first resting within the notch of 

 the first distichals. Anal side remarkably wide. The anal plate, which closely 

 resembles the radials, followed by three rather large plates, and these by 

 three smaller ones and an elongate plate at each side, which latter rise to ■ 

 the top of the plates of the third row, so that the second and third rows to- 

 gether contain eight plates. This arrangement, however, is not invariable; 

 there are some specimens in which these rows have five plates each, and the 

 plates above, on approaching the tegmen, form a rounded, conspicuous ridge, 

 which connects with the anus. The course of the ambulacra is indicated in 

 the casts by well marked ridges, which branch twice upon the surface, 

 and show that there was a third bifurcation in the calyx. Ventral disk 

 hemispherical, composed- of rather uniform pieces of moderate size. Anus 

 subcentral. 



Horizon and Locality. — Upper part of Niagara group ; Chicago, Ills. 



Eemarks. — We have carefully compared Miller's types of his "Sacco- 

 criniis" pyriformis with the types of Periechocrinus urniformis, both in the 

 collection of Mr. Egan of Chicago, and came to the conclusion that the dif- 

 ferences pointed out in the descriptions are not constant, and are to a large 

 extent imaginary. 



(?) Periechocrinus brnatus (Hall). 

 Plate L. Figs. 3a, b, and Plate LI. Fig. 7. 



1875. Saccooritms ornaUis — Hall; Geol, Rep. Ohio, Palseout., Vol. II., p. 126, Plate 6, Kgs. 7 to 9. 

 1881. Periechocriims oriiatiis — "W. and Sp. ; Revision Palajocr., Part II., p. 132. 



Sjn. Saccocriims Benedieti — S. A. Miller ; 1892, Adv. Sheets IStli Rep. Geol. Surv. Indiana, p. 29, 

 Plate 5, Figs. 1 and 2. 



A smaller species than the preceding one. Calyx obovate ; the dorsal cup 

 elongate urn-shaped, obscurely pentangular in the upper portions, the rays 

 at the arm bases widely separated, especially upon the posterior side. Plates 

 highly elevated, subcorneal, with deeply channeled sutures ; the surface cov- 

 ered with coarse rugosities or irregular protuberances, meeting in the centre 

 of the plates, and passing out to the edges. 



Basals rather large, forming a moderately spreading cup. Eadials and 

 costals higher than wide, gradually decreasing in size; the former consid- 

 erably larger than the costals. Distichals free from above the third plate. 

 Arm structure unknown. Interbrachials in five rows ; the first plate as large 

 as the first costal ; there are two in the second range, and five in the three 



