R. We H. ROW—REPORT ON THE SPONGES: CALCAREA. 199 
All the three facial rays are of approximately the same length and diameter, 
the basal being sometimes slightly longer than the two oral. All the facial 
rays are slightly curved ; they taper slowly for the most part of their length, 
and are usually somewhat abruptly pointed. 
Fig. 2.—Spicules of Grantilla quadriradiata, all x 60. 
(ii.) Triradiates (Text-fig. 2, a, b).—The subgastral elements of the in- 
articulate tubar skeleton are very largely prochiacts (text-fig. 2, a) of typical 
form, with a few intermediate forms, and true sagittal triradiates with them 
(text-fig. 2, 0). The subdermal skeleton also contains a very considerable 
number of prochiacts, though here the number of sagittal triradiates is 
proportionately very much larger, forming about one-half of the total number 
of subdermal spicules. Intermediate forms also occur fairly numerously, so 
that the prochiacts do not on that side amount to more than one-third of the 
total number of subdermal triradiates. 
The paired rays of both prochiacts and sagittal triradiates are usually 
curved, and frequently are not quite equal, either in length, or inclination to 
the basal ray. ‘This is much more marked in the triradiates than in the pro- 
chiacts. The rays in each case taper gradually for the greater part of their 
length, and rapidly for the distal fourth of their length. 
The basal ray is very much the longest, reaching to as much as three times 
the length of the oral rays, and is quite straight. It tapers gradually for its 
whole length, but somewhat more rapidly in the distal portions. All three 
rays are of the same diameter. 
IG; 
