LOWER HELDERBERG ROCKS. 
103 
Mariacriims nobilissimus (n.s.). 
Plate II. Fig. 1-4; and Plate II A. Fig. 1. 
Body large, obconical below, becoming obtusely pentagonal above by the 
prominence at the base of' the arms. Plates with obscure radiating 
ridges, which become conspicuous near the sutures. Surface finely 
granulose. Basal plates four, wider than long; three pentagonal, and 
one hexagonal and truncated above ; the hexagonal basal plate anterior. 
First radial plates about as long as wide; four lieptagonal, the anterior 
one hexagonal. Second radial plates sometimes longer than wide ; four 
heptagonal and one hexagonal. Third radial plates about as wide as 
long; four heptagonal (?) and one octagonal. Intermediate plates large; 
four on each side of the four regular sides. Anal plates, or interradial 
plates upon the anal or irregular side, nine. Brachial plates two resting 
on each third radial, and each of these succeeded by two others which 
rest successively upon each other, with an intercalated single range of 
three or four small plates between. The third brachial plate on each 
side supports upon its upper edge a double set of plates, the outer ones 
of which on each side support the auxiliary arms, while the inner ones 
support the plates forming the centre or principal arm in direct .suc¬ 
cession, and its subordinate branches. 
Arms composed of double series of alternating plates, which are broader 
than long, slightly interlocking at their inner margins, producing a 
slight groove along the centre of the arm. Every fourth or fifth plate 
on each side becomes thickened on its outer margin, and obliquely 
truncated, giving origin to the lateral branches or armlets. The entire 
arm thus consists of its own articulations proper, and supports a series 
of lateral branches to the number of more than thirty on each side. 
The armlets or fingers are gradually tapering, nearly round, and com¬ 
posed of double series of alternating plates much broader than long, 
and closely interlocking at their wedgeshaped inner margins. Each one 
of these plates supports a tentacle on its outer margin, giving a double 
[ Paleontology III.] 14 
