324 THE VOYAGE OF H.M.S. CHALLENGER. 



terminate in tlie cii-cular swelliug or iu one of the four tubercles, while the prolongation 

 of the principal canal is likewise straight, and terminates close beneath the teeth. 

 Hence I am of opinion that I can with certainty exclude the view that the teeth are to 

 be rewarded as curved principal rays, and maintain the opinion that they are terminal 

 rays of a greatly shortened radial principal. These terminal rays are as a rule rough and 

 straio-ht, and provided with terminal knobs. There are usually four, but three may also 

 occur. Exceptionally an S-shaped curvature occurs, as on PI. XCI. fig. 4. 



The o-astralia are so essentially similar in form and position to the dermalia that no 

 special description is required. I may simply refer to PI. XCI. fig. 2. 



In the parenchyma tolerably regular uncinates of various dimensions occur in great 

 numbers, but extend usually only through half the thickness of the plate. They are all 

 disposed at right angles to the surface. In the uncinates occurring near the dermal 

 surface aU the barbs have their points towards the gastral side, while in the uncinates 

 which lie closer to the gastral side, the points of the barbs are turned round and 

 directed towards the dermal surface. On both surfaces therefore the uncinates would 

 on gentle motion project outwards from the sponge body. The numerous small hexacts, 

 which are for the most part fused to the dictyonal framework, but partly also occur free 

 in the soft tissue, are provided with pointed tubercles, and each of the rays is obliquely 

 pointed at the extremity. Moreover many elegant discohexasters also occur in the 

 parenchyma, and exhibit various forms. Very frequently small rosettes, such as are 

 figured on PL XCI. fig. 6, occur, and each of the moderately short basal rays bears four, 

 five, or six terminals, which are curved in an S-like manner like petals, and knobbed 

 or provided with terminal discs. More rarely forms occur in which the basal rays are 

 somewhat longer and more slender, and are united in a spherical central knot. These 

 bear on their outer extremities from three to four very fine long terminal rays with 

 terminal discs. "Whether the rosettes with long rough basal rays, which are represented 

 on PI. XCI. fig. 7, and which I found here and there in preparations of Chonelasma 

 hamatum really belong to this species and are not merely intrusions, I have lately seen 

 reason to doubt. In any case, however, should they really belong to this sponge, they 

 are of very rare occurrence. 



The structure of the soft parts difi'ers from that described in Chonelasma lamella at 

 most in the greater simplicity of the straight afierent and efferent canals which traverse 

 the plate at right angles (PI. XCI. fig. 2). 



3. Chonelasma dcederleinii, n. sp. (PI. XC. figs. 1-7). 



Among the HexactineUida which were collected by Dr. Doderlein in the Sagami Bay 

 (Japan) there are some irregularly bent plates from 2 to 3 mm. in thickness which are pre- 

 served in the dry state. These are provided with a thin undulating margin, are from 2 to 

 3 cm. in breadth, from 4 to 5 cm. in height, and without doubt were attached to a solid 



