CAULOPHACUS SCHULZEI. 49 
The remaining nineteen specimens, one of which is represented on Plate 9, 
fig. 28, are larger. Their irregularly oval discs are 40-64 mm. long, 34-54 mm. 
broad, and 7-12 mm. thick in the middle. The more or less eccentric and 
oblique stalk is, near its point of insertion, 2.5-7.5 mm. thick and quite rapidly 
attenuated below. The disc is flat, slightly convex or concave. The greater 
part or the whole of the marginal portion of the upper face is convex, so that 
the margin appears slightly bent down. 
The stalk is not intact in any of the specimens, but there are among the 
fragments three rather long stalks with intact lower (distal) end. These are 
30-40 mm. long, curved, particularly near the base, and 2 mm. thick (at the 
lower end) to 3.3 mm. (at the upper end). One of these stalks (Plate 9, fig. 28) 
appears to have been torn off the larger specimen. In the photograph this 
stalk is artificially attached to it. 
The specimens examined by Wilson (loc. cit., p. 43, Plate 4, fig. 3) were 
similarly composed of a calyculate, flat, or somewhat convex disc-shaped body, 
22-50 mm. in diameter, and a stalk invariably broken. 
The colour of all the specimens in spirit is brownish gray. 
General structure. Remnants of a superficial membrane supported by the 
lateral pinule-rays can be made out both on the dermal and the gastral faces 
of the sponge. This membrane lies on both sides, 70-100 » above the level 
occupied by the lateral rays of the hypodermal and hypogastral pentactines. 
In the intervening space shreds of tissue are observed, indicating that in life 
this zone was occupied by a network of trabeculae. Below the level marked by 
the lateral pentactine rays subdermal and subgastral cavities occur, which lead 
into canals extending more or less transversely, often through the greater part 
of the thickness of the whole disc (Plate 8, figs. 28, 29; Plate 9, fig. 32). The 
entrances to these canals are clearly visible, both on the dermal and the gastral 
face of the disc-like body. Where the superficial membrane is still present, 
they are covered by it; where this membrane has been lost, as is the case on 
nearly the whole of the surface in most of the specimens, they are freely exposed. 
The apertures of the dermal face resemble in shape and arrangement those of 
the gastral face, but are on the whole somewhat larger. The largest are always 
formed on the central part of the disc. Towards the margin they become 
smaller. Their distance from each other is in proportion to their size; the 
marginal ones lie much closer together than the central ones. The largest cen- 
tral apertures are 0.8—4 mm. wide, their width being, on the whole, in proportion 
to the size of the specimen. Apertures over 3 mm. in diameter have been 
