442 
THE VOYAGE OE H.M.S. CHALLENGER. 
parts the borders of the facets are raised into an elevated margin. The grooves are 
provided with a proper wall, consisting of colourless fibres, densely ensheathed in a brown 
cell-substance. Within each hexagonal area rises a low cushion-like prominence, into 
which bundles of spicules rising vertically from the base of the sponge enter in columnar 
groups, and radiately project beyond the surface. 
The fibrous cortex is sharply distinguished from the choanosome, its fibrous tissue is 
continued inwards as the walls of the canals. 
Spicules. — I. Megasclere. 1. Tylotoxea, arranged in bundles, which rise vertically 
from the base. 
II. Microscleres. 2. Spheraster. 3. CJiiaster, actines cylindrical, numerous, 
curved, or minutely tubercled. 
Colour, — Black, in spirits. 
Habitat. — Antilles. 
Remarks. — The alliance of this sponge with TetJiya has been pointed out by Carter 
iloc. cit. supra). 
Genus 3. Magog. ^ 
Tethyidse in which the rhabdus spicule is an oxea, which is confined to the choano- 
some. 
From Carter’s description it would appear that the oxeas are not arranged in 
radiating spicular fibres. In this and the presence of chones the genus differs widely 
from Tethya. 
Magog sacciformis (Carter). 
Ghondrilla sacciformis, Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. iii. p. 299, pi. xxvi. figs. 
9, 11, 12, 1879. 
Sponge. — Massive, depressed, produced into cylindrical hollow lobes, sessile. Surface 
even. Pores the single openings of chones uniformly distributed ; oscules situated at 
the ends of papillae scattered generally over the surface, or singly terminating the 
saccular lobes. 
Spicules. — I. Megasclere. 1. Oxea, fusiform, curved, I'O by 0’028 mm. 
II. Microsclere. 2. Spheraster, centrum very large ; actines correspondingly short, 
numerous, conical, rounded off near the end, or truncate, or slightly expanded and 
minutely tubercled ; centrum 0’09 mm. in diameter, actines 0'013 mm. long, total 
diameter 0*116 mm. 
1 Magog, the name of a giant, popularly represented as armed with a “ morning star.” 
