SPONGES. 95 



have uniformly granular cytoplasm and large, well-defined nuclei, each typically with 

 a single darkly-staining nucleolus. 



Of this remarkable sponge eight specimens were found, anchored in the soft mud 

 at the bottom of Tamblegam Lake (a large inlet from Trincomalee Bay) ; but only one 

 was forwarded to Cape Town for more minute investigation. 



The species is evidently nearly related to Tetitta dactyloidea (Carter), which that 

 author records (20, 34, 43) from the south-east coast of Arabia, Bombay, and the 

 Mergui Archipelago. The principal difference apparently concerns the excurrent canal- 

 system. In T. dactyloidea tbere appears to be a single vent at the summit of the 

 sponge, and Mr. Carter observes that the terminal aperture divides into a number of 

 branches, which, sub-dividing, permeate the mass generally down to its base. In 

 T. limicola, as we have seen, the sponge is very compact throughout, and there are 

 no wide tubes in it, the excurrent canals being very narrow and opening by numerous 

 minute apertures in the floors of somewhat flask-shaped cloacae with slit-like vents on 

 the surface of the sponge. It is highly probable that this arrangement is a special 

 adaptation to the conditions of life, serving to hinder the entrance of the very fine 

 soft mud, in which it lives, into the interior of the sponge ; even as it is, a considerable 

 amount of mud may be seen in the excurrent canals just beneath the floor of the 

 cloaca. 



R.N. 70 (one of eight specimens from Tamblegam Lake, Trincomalee). 



Craniella, Schmidt. 



The ectosome is differentiated into an inner fibrous layer, containing more or less 

 radially arranged cortical oxea, and an outer collenchymatous layer excavated by 

 large subdermal cavities. 



Craniella elegans, n. sp. Plate IV., fig. 1. 



Sponge free, irregularly spherical. Surface covered with close-set conuli ; hispid 

 with brushes of spicules projecting from the conuli ; minutely reticulate between the 

 conuli. Vents not visible in the type specimen. Pores in the thin dermal membrane 

 stretched between the conuli. Colour, in spirit, purplish grey externally, yellow 

 internally. Greatest diameter of type (R.N. 193) about 20 millims. Consistence 

 firm and compact. 



The main skeleton consists of stout bundles of spicules radiating from a central 

 " nucleus" and ending in the brushes which project from the surface conuli (Plate IV., 

 fig. 1). These radiating bundles (r.b.) are separated from one another by fairly wide 

 intervals, and are composed of large oxea, with anatrioenes and protrisenes. The cladi 

 of the anatrieenes are, for the most part, situated in the outermost part of the 

 choanosome, just beneath the cortex, while those of the protrieenes mostly project 

 beyond the surface of the sponge in the hispidating brushes. The special cortical 

 skeleton is, as usual in Craniella, confined to the inner, fibrous layer of the cortex, 



