MELOCRINID^. 297 



small interdistichal. The surface of these plates is covered by radiating 

 rido-es and nodes ; while that of the succeeding ones is without ornamenta- 

 tion, and the plates are transversely arranged. The brachials of the fourth 

 order consist of six plates, those of the succeeding ones of five, rarely four 

 (so far as observed) ; all transversely arranged, and suturally connected with 

 their fellows of opposite sides, forming ^ye long tubular, arm-bearing trunks. 

 The arms of this species are more slender than in the preceding one, and 

 slightly more tapering, the pinnules longer ; they are flattened on the back, 

 and the surface is corrugated. Interradial spaces composed of about twelve 

 plates arranged in two longitudinal rows, the plates alternating with one 

 another. The anal interradius and ventral disk are not visible in the speci- 

 mens. 



Horizon and Locality. — Schoharie Co., N. Y. ; Lower Helderberg group. 



Ti/pes in part in the American Museum of Natural History, New York. 



MelOCrinuS bainbridgensis Hall and Whitfield. 

 Plate XXII. Figs. 4a, h, c, and Plate XXIV. Fig. 5. 



1875. Melocrimis {Ctenoc7'imis) bainbridgensis — Geol. Surv. Oliio, Palseont., Vol. II., p. 158, Plate 13, 



Pigs. 2 and 3. 

 1881. Melocrinus bainbridgensis — W. and Sp. ; Uevision Palaeocr., Part II., p. 121. 



Syn. Melocrinus Glarkei Williams; 1882, Proceed. Acad. Nat. Sci. Phila., p. 31. 



Specimens above medium size. Dorsal cup as high as wide, rather rap- 

 idly spreading ; sides somewhat convex ; cross-section pentangular. Plates 

 slightly elevated, beveled at their margins ; the middle part a little depressed, 

 and covered with a system of confluent granules ; the suture lines grooved. 



Basals forming a low cup with a small rim around the lower margin, 

 which is notched at the interbasal sutures ; axial canal pentalobate. Radials 

 and costals wider than long, decreasing in size upwards. Distichals 3 X 10, 

 those of the same ray in contact laterally, interdistichals not being repre- 

 sented; the proximal one less than half the size of the second costal, and as 

 long as wide ; the two others much shorter. The third plate, which is axil- 

 lary, supports upon its inner face the next order of brachials, at the outer 

 the proximal arm which is free from its origin. The brachials of the suc- 

 ceeding orders also consist of three pieces, which are transversely arranged, 

 and those of the same ray are laterally connected, forming trunks from 

 which arms are given off at every third plate. The trunks taper upward, and 

 are deeply grooved along the line of contact of the two branches. Arms 



38 



