R. W. H. ROW—REPORT ON THE SPONGES: NON-CALCAREA. 343 
Sub-Family Eoryoninz. 
Desmacidonide in which some of the megascleres take the form of spined 
styli, originally developed as echinating spicules of the skeleton fibre or 
projecting at right angles from the substratum. 
MYXILLA ISODICTYALIS (Carter). 
Synonymy :— 
1882, Halichondria isodictyalis, Carter (4). 
There is a small fragment of this species in the collection, which, though 
extremely small and fragmentary, is easily recognizable as this species by its 
skeleton arrangement and spicules, which agree with Carter’s original 
description in every particular. 
Locality. Suez mud-flats. 
Dhestribution. Red Sea, Acapulco. 
MyYXILLA CRATERA, n. sp. (PI. 8%. fig. 13; Text-fig. 20.) 
This new and remarkable species is represented in the collection by a 
considerable number of specimens, all of which are very similar in external 
appearance. They each consist of a cushion-like mass of rather irregular 
shape and varying size, attached to some foreign body by a large base. The 
largest specimen measures 50 mm. by 32 mm.,and is 25 mm. high from base 
to summit. 
The surface is covered thickly with small crater-like projections, which are 
pore-areas, and which measure about 2 mm. to 3 mm. in diameter on the 
average. 
Each pore-area is raised on a more or less circular wall from the regular 
surface of the sponge, and this wall is usually about 0°7 mm. high. Inside 
the cone thus formed, but rather below the top of the wall, a membrane is 
stretched, in which are pierced a very large number of pores of small size. 
(There are sometimes hundreds of minute pores in a single pore-area.) 
Below the membrane is a large cavity, above the surface of the sponge, and 
occupying almost the whole of the inside of the crater-like process. At the 
level of the general surface of the sponge there is another membrane, this 
time apparently sphinctrate, which can close (presumably) the entrance to 
the inhalant canals, which run directly down from these “ pore-cones” into 
the interior of the sponge. 
These pore-areas, as can be seen in the photograph (PI. 37. fig. 13), are 
packed together thickly over the whole surface of the sponge. They extend 
right down the sides of the cushion to the base. | 
The oscula are small, and are provided with special cones like the pore- 
