F. R. Cowper Reed—Haverfordwest Fossils. 209 
are rather strong arched longitudinal strie, indicating by their pointed 
lanceolate arrangement and invasion of the base of the preceding 
segment that the leaves overlap each other successively. There is 
occasionally a short stalk present in the basal and apical segments 
(and paired lateral spines may be present). ‘The celluliferous face of 
each segment is flat and shows the one layer of cells arranged in 
rather irregular rows diverging in a fan-shaped manner from the base ; 
the median rows are more or less subparallel and continuous from 
leaf to leaf without a break, and are composed of short cells of equal 
size, very oblique to the surface; the lateral rows diverge more 
strongly to the sides and are irregular, and the cells are subequal in 
size, somewhat larger, shorter, and less oblique to the surface, so as 
to form a close polygonal mosaic ; in a leaf 5 mm. long, 15-20 cells 
may be counted round each lateral margin, and 10-16 across the 
widest part of the leaf, the number varying with the size of the leaf, 
but the size of the cells remains fairly constant. 
Dimensions : 
I ; Length. Width. 
Basal leaf ... os or ra Be er) te 3:00 mm. 
Middle... a se on eats RASOO nt 2°75mm. 
Apical be se 505 a SoG WD) rie 1:60 mm, 
101 
ae aa aie ae | (posterior part) 2°50 2-75mm. 
eee s i. ca (anterior part) 4:00 3°00 mm. 
or compound nature) 
Middle leat 3°75 2°75 mm. 
Apical 2°25 1-25mm. 
IME. 
Posterior leaf... 233 oe si a°25 oe 4:25mm. 
Anterior ... - ee ass an 5°25 sas 4:00 mm. 
In No. II the basal leaf shows a transverse constriction which may 
indicate that it is composed of two almost completely fused leaves, or 
the constriction may be of a secondary nature, which would ultimately 
result in the division of the one leaf into two and thus increase 
the number of segments of the zoarium. 
Isolated leaves: length, 4:0-5:0mm.; width, 2°0-2:25 mm. 
There are two other specimens (Pl. VI, Figs. 8—-9a) which 
probably represent a variety or another and later stage of growth 
in the same species. One of these consists of a modified leaf of the 
same type as the foregoing, with the usual medianly ridged epitheca 
on one side and the radiating rows of cells on the other. But instead 
of being of a lanceolate shape, it is subrhomboidal and considerably 
broader than usual; the two longer sides meet at the apex at about 
75°, and the two shorter ones at the base at rather more than a right 
angle; the base is produced into a short point, but the lateral angles 
are furnished with long straight tapering spines directed at mght 
angles to the axis of the leaf, and marked by a median groove, 
but apparently not celluliferous. In length they are equal to about 
two-thirds the greatest width of the leaf. At the apex of the leaf we 
see attached in the usual way a very small slender lanceolate leaf of 
about half the length of the maiz one. Length of large leaf, 5-0 mm. ; 
maximum width of ditto, 4.5mm. ; length of small leaf, 2°25 mm. 
DECADE V.—VOL. IvV.—NO. V. 14 
