TETRAXONIDA 



279 



Spicules scattered between, but in most of the present specimens (Fig. 12 b) the 

 multispicular fibres are resolved into anastomosing systems of smaller fibres. There are, 



Fig. 12. Dasychalina validissima (Thiele). a, b, sections at right angles to surface 

 (a is from holotype); c, dermal skeleton. All x 7J. 



however, all gradations between these two extremes. The oxea measure o- 15-0-32 mm. 

 long. 



Distribution. Calbuco ; Straits of Magellan. 



Genus Callyspongia, Duchaissang and Michelotti. 



Callyspongia fortis (Ridley) (Figs. 13, 14). 



Siphonochalina fortis, Ridley, 1881, p. iii, pi. x, fig. 3. 



Occurrence. St. WS72: Falkland Islands, 95 m.; St. WS 83 : Falkland Islands, 137-12901.; 

 St. WS 84: Falkland Islands, 75-74 m.; St. WS 86: Falkland Islands, 157-147 m. 



Diagnosis, Sponge sub-ramose to lobose; surface minutely conulose; oscules large, 

 conspicuous, situated on crater-like projections or with margins level with surface, in 

 all cases leading into deep cloacae receiving large exhalant canals which penetrate body 

 of sponge ; pores apparently scattered in meshes of dermal skeleton ; skeleton differen- 

 tiated into main and dermal ; main skeleton consisting of a coarse-meshed network of 

 stout spongin fibres, often 0-3 mm. thick, containing an axial row of spicules, multi- 

 spicular in primary fibres, unispicular in secondary fibres; meshes of main skeleton 

 ranging from 0-4 to 1-2 mm. across; dermal skeleton a tangential network of fibres 

 differentiated into primary, secondary and tertiary fibres; primary fibres stout, of 

 similar dimensions to those of main skeleton; mesh usually triangular, but may be 

 quadrate or polygonal and divided into secondary and tertiary meshes; dimensions 

 of latter usually no more than a spicule length across ; spicules oxea, straight, o-o66 by 

 o-oo6 mm. 



Remarks. The species is characterized by its external form and by the small size of 

 its spicules. 



The inadequacy of Ceraochalina, as a genus for the reception for all Chalininae in 

 which the spicules are vestigial, is shown by one specimen in which the fibres of the 



6-2 



