296 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
Family GEODIID4. 
Astrotetraxonida in which the characteristic microsclere is a sterraster 
forming a dense cortical layer. 
GEODIA MICROPUNCTATA, n. sp. (Pl. 35. fig. 5, Pl. 40. fig. 24; Text- 
fig. 2.) 
This new species is represented in the collection by several incomplete 
specimens, all but two of which consist merely of pieces of the sterraster 
crust, without any of the interior of the sponge. The two species in which 
the choanosome is present as well as the cortex are both apparently fragments 
broken off from larger individuals. They are irrgeular and massive in shape, 
and each presents a relatively large surface of exposed choanosome where 
they have been torn away, either from their support or from the rest of the 
specimen. The largest specimen measures about 
100 mm. long by 90 mm. wide, and the smaller 
about 60 mm. by 55 mm. ; each of the specimens 
being about 30mm. to 35 mm. thick. There is no 
foreign matter whatever attached to the larger 
specimen ; but the smailer is growing over and 
partially enclosing a group of mussels (one of which 
8 is shown in PI. 35. fig. 5), and two of the fragments 
of sterraster crust are also attached to mussels. 
The surface of the sponge is gleaming white 
and is perfectly smooth, no spicules whatever 
projecting from it. It is pierced by a number 
of small circular oscula, irregularly scattered over 
the surface of the sponge and varying in size 
vis from 0:2 mm. to 0:8 mm. in diameter. On the 
e larger specimen the oscula are somewhat few 
El ices and do not grow to any large size, and this is 
the case with the greater portion of the surface 
of the small specimen. There occurs on the 
| smaller specimen, however, a portion of the surface 
Fig. 2.—Geodia micropunctata. of the under side of the sponge, and here the oscula 
A and B x60; C,D,and are many in number and of comparatively large 
E x1000. size (see Pl. 85). This probably furnishes the 
explanation of the entire absence of large oscula 
from the large specimen, as no portion of the under surface is present in 
that specimen. In many cases there is present a clearly defined oscular 
sphincter membrane, which is frequently more or less closed. In all 
