LOWER HELDERBERG ROCKS. 
11 a 
PLATE III A. 
Fig. 2. A fragment of the column of this species. 
PLATE III E. 
Fig. 3, 4, 5, 6 & 7. Several fragments of columns 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 : Helderberg mountains and Schoharie. 
Platycriims plumosus (n. s.). 
Plate IV. Fig. 1-5. 
<4 
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 : surface 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 lieptagonal, 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. 
Column round, very slender; consisting, near the body, of alternating 
larger and smaller joints, each large joint giving off a series of five 
long slender branchlets, which closely embrace the body and base of 
the arms, reaching nearly to the extremities of the arms themselves. 
[ Palaeontology III.] 15 
