CALYCOSILVA CANTHARELLUS. 
69 
(Plate 6, fig. 18) this involuted portion of the body, which extends quite to the 
centre, lies in front. 
The lower side of the plate-like body is the dermal, the upper, the gastral. 
They are identical in structure and both formed by a transparent membrane 
destitute of larger apertures. The entrances to the large afferent and efferent 
choanosomal canals are seen through this membrane. In some places where 
the superficial membrane has been lost these canal-entrances are bare. 
The six specimens of C. c. var. megonychia are fragmentary plate-like parts 
of the body proper of the sponge. Parts of some of these attain a thickness of 
8 mm., and these thin out to a rather fine margin at one side. The largest of 
these fragments is 49 mm. long and 35 mm. broad. 
The twenty-four fragmentary specimens of C. c. var. simplex (A) are parts 
of plates with a maximum length and breadth of 50 mm., and are at their thickest 
point 4-6 mm. thick. One of these fragments formed a central part of a sponge; 
to this the upper part of a stalk is attached. The surface has the same character 
as in C. c. var. helix, the only difference being that much more of the superficial 
membrane has been lost and that some slender spicules protrude from it to dis- 
tances of 10 mm. or more. I am inclined to consider these hair-like spicules as 
foreign. 
The single, specimen of C. c. var. simplex (B) (Plate 5 , fig. 10) has the shape 
of a pipe. It is traversed by the fragment of a large foreign spicule, probably 
a root-tuft spicule of a hyalonematid. This foreign spicule, which forms the 
base of attachment is — for a length of 39 mm. — coated by a thin layer of the 
sponge. Thus a cylinder 39 mm. long and 2-3 mm. thick, appearing as the stem 
of the pipe, is formed. This stem is to be considered as the stalk of the sponge. 
From one end of this stalk, which probably lay horizontally on the sea-bottom, 
a structure 9 mm. thick and 15 mm. long, resembling the bowl of the pipe, 
arises at an angle of about 106°. This part of the specimen is to be considered 
as the upper end of the stalk and part of the body proper of the sponge. 
Colour. All the specimens are grayish brown. C. c. var. helix has a more 
grayish colour, C. c. var. megonychia and simplex are more brownish. The speci- 
mens of C. c. var. megonychia are rather darker than the others. 
General structure. A fine superficial membrane uniformly covers the 
dermal surface of the stalk and the dermal and gastral surfaces of the body 
proper. This membrane is supported by the paratangential rays of the pinules 
and perforated by pores which lead into a superficial cavity, 60-90 /j. high (radial 
dimensions), and traversed by numerous fine trabeculae. This cavity is limited 
