R. W. H. ROW—REPORT ON THE SPONGES: CALCAREA. Pals 
Measurements of a series of triradiates is given below (in mm.) :— 
Paired rays. Basal ray. Diam. at base. 
Gastrall cortex) tices «cso 6 ae 0:19 O-4 0:025 
» 0195 0:21 0:03 
o 0:2 0:25 0:016 
os O15 015 0:025 
Dermal cortex wave cscs 0:24 0:076 0:015 
o 0:22 0-091 0:015 
~ (iii.) Spicular fibres——The fibres are composed of remarkable triradiates 
(text-fig. 8,¢), usually having their oral rays reduced to a small triangular 
head at the end of the basal ray. The only other calcareous sponge 
having spicules of this shape is Grantiopsis cylindrica, Dendy, one of the 
Staurorrhaphide, in which the spicules of the articulate tubar skeleton are 
reduced to an exactly similar form. 
These “ nail-spicules,” as I propose to call them, form long fibres extending 
through the whole width of the chamber layer, and arranged radially 
or very slightly inclined to the radial direction. A cross section of a 
fibre will nearly always show from 3 to 5 spicules, four being the most 
frequent number. At the gastral ends of the fibres the “ nail-heads,” 7. e. the 
vestigial paired rays, show a tendency to increase their size, and also 
occasionally the spicules at the sides of the fibre have enlarged “heads.” 
It is very frequent, in this case, to find that one of the paired rays is 
developed much more than the other. 
The length of the basal ray varies from 0°18 to 0°22 mm., and its diameter 
from 0:003 to 00035 mm. The head typically measures 0:008 to 0:01 mm. 
in diameter, but individual oral rays have been noticed as long as 0°02 mm. 
When the length of the oral rays is sufficiently great to enable their diameter 
to be measured, they are found to be equal in width to the basal ray. 
The single specimen in the collection was olsaun en! at Tella Tella Kebira. 
Distribution. Red Sea. 
BIBLIOGRAPHY. 
(1) BowErpank, J.S.—“ Monograph of the British Spongiade.” Ray Society, 1864-1882. 
(2) Denpy, A.—“ Studies on the Comparative Anatomy of Sponges. The Structure and 
Classification of the Calcarea Heteroccela.” Q. J. M.S. vol. xxxy., 1894. 
LINN. JOURN.—ZOOLOGY, VOL. XXXI. 17 
