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. rnegonychia 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 nmi. 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 incUned to consider these hair-Uke 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. rnegonychia 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 yu high (radial 

 dimensions), and traversed by numerous fine trabeculae. This cavity is limited 



