LOWER HELDERBERG ROCKS. 113 



PLATE III A. 

 Fig. 2. A fragment of the column of this species. 



PLATE III B. 

 Fig. 3, 4, 5, 6 & 7. Several fragments of column* of different sizes, each showing the small 

 attached rootlets, or the points from which they have been broken off. 



Geological position and locality. In the lower part of the shaly limestone of the 

 Lower Helderberg group : Ilelderberg mountains and Schoharie. 



Plat}ci1nas pluuiosus ( n. s.). 



Plate IV. Fia. 1-5. 



Body small, cupform, expanding and subpentagonal at the bases of the 

 arms : surface finely granulated. Basal plates three, wider than long, 

 very thin ; point of attachment for column very small. Costal or first 

 radial plates six, large, thin, wider than long, deeply excavated upon 

 the upper margin for the insertion of the second radial plate and the 

 base of the arms : svu'face prominently convex in the middle, below 

 the second radial. Second radial plates small, short, subquadrangular, 

 filling the excavation in the upper edge of the larger first radial, and 

 not extending as high as the upper margin. Anal plates two [visible] ; 

 the first large heptagonal, the second much smaller and hexagonal. 

 First brachial plate pentagonal ; vertical sides short ; base straight ; 

 two upper sloping sides supporting the bifurcating arms. 



Arms simple from this point to their extremities, more than five times as 

 long as the body : joints numerous, wider than long, each one giving 

 origin to one or two tentacles from each side. Tentacula long, slender ; 

 joints angular, nearly twice as long as wide : surface granulated like 

 the body and arms. 



Proboscis about two and a half times as long as the body, composed of 

 hexagonal or irregular plates, which become smaller towards the 

 summit. 



CoLCJiN roijnd, very slender; consisting, near the body, of alternating 

 larger and smaller joints, each large joint giving off a series of five 

 long slender branchlcts, which closely embrace the body and base of 

 the arms, reaching nearly to the extremities of the arms themselves. 



[ PAI,.«ONTOL0aY III.] 15 



