84 PALiEONTOLOGY OF NEW-YORK. , 



124. 2. POTERIOCRINUS GRACILIS. 



Pl. XXVIII. Figs. 2 a, b, c, d, e,f. 



Body small, obconical, gradually expanding above, surmounted by long slender bi- 

 furcating tentacula, which are not fimbriated. 



The pelvic and costal plates are precisely in form like those of the last species, but the 

 brachial plate is much shorter, and but five-sided ; the attachment of the fingers upon the 

 upper side is by a broad plate. The surface of the plates is finely granulated, appearing 

 nearly smooth to the naked eye. The fingers are thrice bifurcated above the hand-joints, 

 and, towards their termination, appear to be covered by a muscular integument. The column 

 is proportionally much larger than in the last species, and is composed of thin even plates, 

 which are closely adhering at the margins, and sometimes appear striated longitudinally, 

 the whole presenting an appearance as if covered by an integument. A few of the upper 

 joints of the column, only, have been seen in a single specimen ; the last joint adheres 

 closely to the base of the pelvis. This species differs, likewise, in the much greater length 

 of the tenlacula, which are somewhat unequally bifurcated above, and composed of long 

 smooth joints, while in the previous species the fingers are tentaculated and shorter. 



The irregular intercostal (interscapular of Miller) plate is distinguishable in this species, 

 showing that it is clearly referable to this genus. 



Fig. 2 a. A specimrn of the natural sizn, which is broken off just below the last joint of the column, 

 which adheres closely to the pelvis. The tentacula are broken off above, before reaching 

 their termination. 

 Fig. 2 b. The same enlarged, showing more clearly the arragement of the plates, and the situation of 

 the intercostal plate. 

 E. Pelvis. 

 r. Costal plates. 

 J. Irregular intercostal plate. 

 H. Scapular plate. 

 Fig. 2 c. The body of another specimen, with a few of the last joints of the column attached. 

 Fig. 2 d. The same enlarged, showing the intercostal plate and the structure of the column. 



Position and locality. This species has been found only in the soft shaly layers near the 

 base of the Trenton limestone, at Middleville, Herkimer county. 



(From the Collections of Mr. Wadleigii and Dr. Emmons.) 



