288 Transactions. — Zoology. 



distal cones protrude. This sponge forms a most interesting 

 link between the two genera Sycon and Ute. In spite of its 

 striking peculiarity, I think it better to place it in Sycon, from 

 which received definitions do not exclude it, than to establish 

 a new genus. 



The sponge is solitary, or forms small clusters. It is about 

 20mm. in height and 7mm. in breadth. There is a well- 

 developed gastral cavity and a short peristome. There is a 

 dermal cortex containing several layers of large oxeote spicules, 

 longitudinally disposed, and it is pierced by the projecting 

 distal cones of the radial chambers. The tubar skeleton con- 

 sists of sagittal 3-radiate spicules, and the well-developed 

 gastral cortex consists of 8-radiates and 4-radiates, the apical 

 rays of the latter projecting into the gastral cavity in the 

 usual way. 



Spicules : — 



Oxea of dermal cortex : These are very large fusiform 

 spicules, tapering to moderately sharp points. l - 18mm. x 

 06mm. 



Oxea of peristome : Thickest near the proximal end ; sharp- 

 pointed. 025mm. x 001mm. 



Oxea of distal cones : Thickest part about one-third of the 

 distance from the proximal end. OTlmm. x 001mm. 



Triradiates of chamber-layer : Sagittal ; sometimes irregu- 

 lar. The basal ray is generally longest in the spicules that 

 immediately underlie the gastral cortex. Greatest size of 

 basal ray, 0-23mm. x 018mm. ; of oral rays, 0-13mm. x 

 0015mm. The oral rays generally curve away from the 

 basal ray, which they leave at an angle of about 110°. Often 

 one of the oral rays is shorter than the other. Sometimes 

 the basal ray is shorter than either of the oral rays. 



Quadriradiates of gastral cortex : Sagittal ; basal ray, 

 - 14mm. x 0-01mm. ; oral rays, O'OSmm. x O'OOSmm. The 

 rays taper evenly to a sharp point. 



All the radial chambers have well-marked chamber dia- 

 phragms, the circular opening in which communicates with 

 the short canal leading through the gastral cortex to the 

 gastral cavity. The chambers are octagonal in transverse 

 section ; the inter-canals quadrangular. 



A specimen containing ova shows frequently two or three 

 ova in one capsule — a rudimentary ovary. 



Dr. Dendy has already pointed out (" Quarterly Journal 

 of Microscopical Science," 1892, p. 168) that Sycon gelatinosiim 

 has a rudimentary pore-bearing membrane stretched between 

 the distal cones, and that a similar membrane in S. boomerang 

 contains a few spicules, showing the path by which the 

 Grantia type ha8 probably emerged from the Sycon ; but the 



