MELOCRINIDiE. 281 



ately concave ; their upper corners but slightly truncated. First costals 

 quadrangular, not more than half the size of the radials, a little wider than 

 long, the lower face convex. Second costals nearly as large as the radials, 

 their upper faces forming an obtuse angle. Distichals one in the calyx. 

 Arms two to the ray ; composed of rather stout quadrangular pieces. The 

 two or three proximal free plates about as long as wide, the others compara- 

 tively longer, and increasing in length upward. The pinnules, which are very 

 stout, almost take the form of armlets ; they are placed far apart, and their 

 joints, like those of the arms, grow longer , upwards. Interbrachials three 

 preserved in the specimen, but having others above ; the arrangement of the 

 plates at the anal side unknown. Column of medium size; the joints 

 rounded at their edges, and decreasing in height downward. 



Horizon and Locality. — Upper part of Trenton hmestone ; Trenton 

 Falls, N. Y. 



T?/pe in the Museum of Comparative Zoology, Cambridge. 



Remarks. — We refer this species with some doubt to Stelidiocrinus^ which 

 it approaches in its general characters ; but as nothing is known of the struc- 

 ture of its anal side, it may belong to a different genus, and perhaps to 

 the Dolatocrinites. 



MARIACRINUS Hall (emended W. and Sp.). 



1859. Hall (in part) ; Palseont. N. Y., Vol. III., p. 104. 



1881. W. and Sp. ; Revision Palseocr., Part IT., p. 114 (Proceed. Acad. Nat. Sci., Phila., p. 288). 



1885. W. and Sp. ; Revision Palseocr., Part III., p. 104 (Proceed. Acad. Nat. Sci., Phila., p. 336). 



1889. S. A. Millee; N. Amer. Geol. and Paleeont., p. 259. 



Calyx obconical, in general aspect resembling Gli/ptocrinus ; interradial 

 and interdistichal spaces large and more or less depressed ; the posterior 

 interradius distinguished by having three plates in the second row; the 

 plates of the rays marked by a strong longitudinal ridge. 



Basals four, small, almost of uniform size. The one facing the anterior 

 side a little the largest and pentangular, the others irregularly quadrangular. 

 Radials and costals of similar size; costals two, the first hexagonal. Dis- 

 tichals two to four. The palmars, of which generally the proximal plate 

 only takes part in the calyx, support the arms. Arms composed of 

 cuneiform pieces, which either remain simple, or give off a few branches 

 to one side. Pinnules given off from opposite sides. Interbrachials rather 

 numerous ; anal side a httle wider, and containing additional plates. Ventral 



36 



