LOWER HELDERBERG ROCKS. 
115 
extend beyond the extremities of the arms and tentacula. Surface of 
branches very finely granulate, where preserved : the surface is for 
the most part much worn. 
This species differs from P. plumosus in the small size and shorter arms, which 
are, however, not entire at the extremities. The joints of the arms are of about the 
same length, but the joints of the tentacula are shorter and less angular. The larger 
joints giving oft' the branchlets are closely arranged near the body, and become 
gradually more separated as the column extends; so that four, five, or more thin 
joints are intercalated between the thicker ones. The little branchlets sometimes 
quite envelope the body and arms, some of them extending beyond the latter as 
represented in the plate. 
Fig. 6. An individual nearly entire, with a small portion of the column from which originate 
the numerous branchlets which surround the body and extend beyond the arms. 
Fig. 7. A similar specimen, preserving more of the column, from which most of the branch- 
lets have been removed. 
Fig. 8. Enlargement of a portion of the column (lower part of fig. 7 ), with the bases of 
the branchlets attached. 
Fig. 9. Enlargement of a single branc-hlct. 
Geological position and locality. In the shaly interlaminations of the Pentamerus 
limestone of the Lower Helderberg group : Jerusalem hill, Litchfield, Herkimer 
county. 
Platycrisius ramulosus ( n. s.). 
Plate IY. Fig. 10 - 13. 
Body small. Basal plates much wider than long. Radial plates compara¬ 
tively large, wider than long, very prominent just below the insertion 
of the second radial plate, and contracted tovrards the upper lateral 
angles. Second radial plate very small. 
Arms bifurcating upon the first brachial plate, and again upon the tenth 
plate above this : joints of the arms wider than long, rounded exte¬ 
riorly, giving origin on their inner margin to strong rounded tentacula ; 
joints of the tentacula apparently a little longer than wide. 
Column round, somewhat large; consisting, near the body, of very thin 
plates, which become thicker at a greater distance. 
