BATOCEINID^. 523 



and is followed by other rows of five or six pieces. Ventral disk paved by a 

 large number of small, smooth, irregular plates, apparently without orals, 

 but small covering and side pieces enter the raarghi. Column near the calyx 

 composed of very short pieces ; central canal of medium size. 



Horizon and Locality. — Niagara group ; Waldron, Ind. 



Remarks. — Megistocrinus marcoucmus and 31. infelix Winch, and Marcy, 

 which Hall has regarded as identical with this species, are probably distinct. 



Periechocrinus marcouanus (Winch, and IMabcy). 

 Plate L. Figs. 7a, b, and Plate LI. Fig. 5. 



1865. Megistocrimts marcouanus — WiNCHELL and Makct; Mem. Boston Soc. Kat. Hist., Vol. I., p. 87, 



Plate II., Fig. 5. 

 1.S79. Syn. of Saccocrimis Christt/i — Hall ; 28tb Eep, N. Y. State Mus. Nat. Hist. (Eevised Ed.), p. 127. 

 1881. Saccoorinus marcouanus — S. A. Millee ; Joum. Cincin. Soc. Nat. Hist, Vol. IV., p. 167, Plate 4, 



Figs. 1, la. 

 1885. Periechocrinus marcouanus {^) — W. and Sp. ; Eevision Palfcocr., Part III., p. 106. 



A very large and elongate species ; the calyx sometimes reaching a 

 length of 75 mm. by about 40 mm. in width across the arm bases; form 

 subovoid, the width greatest at the top of the second costals, whence it con- 

 tracts to the third distichaLs, there expanding again to the arm bases. Inter- 

 brachial and interdistichal areas somewhat flattened or faintly depressed, 

 producing a sort of angularity along the median line of the radial series, 

 without forming an actual ridge until close to the arms. Surface of plates 

 smooth, the suture lines not grooved. 



Basals comparatively small, forming a saucer-shaped, hexagonal cup. 

 Eadials and costals of nearly the same size and of similar form, their lat- 

 eral faces concave to receive the convex sides of adjoining interbrachials. 

 Second costals as long as the first, and nearly as wide ; the upper and lower 

 faces in both of them narrow ; the upper sloping sides longer than the lower. 

 Distichals three, decreasing in .size upwards ; the first nearly as long as the 

 costals, and almost as wide, its upper face quite narrow ; the second of the 

 same proportions but smaller ; the third much shorter. Palmars numerous, 

 comparatively small, shorter than wide, those of the same divisions in lateral 

 contact. Arms four to the ray, arranged in pairs ; their first bifurcations 

 close to the calyx. Interbrachial spaces long and narrow ; they consist of one 

 plate in the first row, followed by from ten to twelve ranges of two plates 

 each, which meet the plates of the tegmen. Anal interradius very wide ; 

 first anal plate a little shorter than the radials, but wider at the upper face ; 



