EEPOET ON THE TETRACTINELLIHA. 
255 
Spicules. — I. Megascleres. 1. Somal oxea, 3'57 by 0’058 mm. 2. Cortical oxea. 
3. Orthotrisene, rhabdome 3 '2 13 by 0 ‘05 5 mm., cladi 0'36 mm. long. 4. Protrisene, 
rbabdome 3‘57 mm. long, cladi O’l mm., chord 0'097 mm. long. 5. Anatriaene, rhab- 
dome 4‘81 mm. long, cladi 0'084 mm., chord 0'071 mm. long. 
II. Microscleres. 6. Sterraster, spherical, 0’065 mm. in diameter. 7. Somal 
pycnaster, actines short, cylindrical, truncate, O’Ol mm. in diameter. 8. Subcortical spher- 
aster, centrum fairly large, actines numerous, conical, minutely spined near the end, 
0'032 mm. in diameter. 9. Choanosomal oxy aster, actines not numerous, conical, 0'04 mm. 
in diameter. 
Colour. — Cream-yellow in the dried state. 
Habitat. — The more or less cup-shaped specimen (pi. vii. figs. 1, 2, Bowerbank, 
vol. iii., op. cit.) is from the island of Fulah and Unst, in “ deep water”; for the oval 
specimen (pi. vii. figs. 3, 4, Bowerbank, vol. iii., op. cit.) no locality is cited. 
Remarics. — The measurements of spicules are taken from the original type figured by 
Bowerbank from the island of Fulah and Unst. It differs in some respects from the 
second (oval) specimen figured by Bowerbank, particularly in the absence of spherasters. 
The material at my disposal is, however, insufiicient for the discussion of their identity. 
In the type specimen a few small, apparently uniporal, oscular chones occur scattered 
in an ill-defined group in the interior of the cup. 
Section 1. Pantoeosa. 
Species possessing both somal and cortical oxeas, and anatrisenes or protrisenes, or 
both, in addition to orthotrisenes or dichotrisenes. 
Cydonium cooksoni, n. sp. 
Sponge ij ). — Cortex 0‘415 mm. in thickness, ectochrote very thin. Pores in sieves 
overlying incurrent chones. Oscules (?). Surface hispidated by cortical oxeas and somal 
oxeas and protrisenes, the last two protruded for a distance of 1 ‘8 mm. 
Spicules. — I. Megascleres. 1. Somal oxea, 1'83 by0‘041mm. 2. Cortical oxea, 
0'129 by 0‘004 mm. 3. Orthotrisene, rhabdome 1‘6 by 0'0645 mm., cladi 0‘24 mm. long. 
4. Protrisene, rhabdome fusiform, 2‘38 by 0*075 mm. close to the cladal origin, and 
0*0129 mm. where thickest. 
II. Microscleres. 5. Sterraster, spherical, depressed, 0*0774 by 0*066 mm. 6. Somal 
spheraster, minute, centrum comparatively large, actines short, cylindrical, with rounded 
ends, 0*001 to 0*006 mm. in diameter. 7. Subcortical spheraster, centrum large, pro- 
