158 llALME. 



from the Neighbourhood of Port Phillip Heads, South Australia (con- 

 tinued)," Annals and Magazine of Natural History, ser. 5, vol. xv. p. 212 



(1885). 



The ordinary shape of this species is that of a more or less irregiJar bulb, 

 from which excrescences often arise ; these attain in some specimens a digitate 

 shape : and sometimes the whole sponge consists entirely of digitate processes 

 which vary in length from 70-120 raillim. ; these are cylindrical, 12-18 millim. 

 thick, and have a circular transverse section. Earely the sponge expands in 

 the shape of a lamella, attached by a small base. The largest bulbous speci- 

 mens attain a diameter of 60 millim. The sponge is grey, with a slight violet 

 tinge when alive ; in spirit and dry it is grey, and has the colour of the sand 

 which forms its cortex. 



The whole sponge consists of a honeycomb-like reticulation surrounded 

 by a dermal lamella. The latter is the only portion visible from outside. 

 It is perforated by numerous pseudoscula. The appearance of the other- 

 wise smooth surface depends on the distribution, shape, and size of these 

 apertures. In some specimens they are circular, 2 millim. wide, aud 3-4 

 millim. apart ; in others smaller and further apart, particularly in the basal 

 portion of the sponge. Sometimes they are larger, quite close together, and 

 polygonal. They rarely equal the cells in the honeycomb below in size. In 

 this case there is no proper dermal lamella. These pseudoscula lead into the 

 vestibular lacunae — the cells of the honeycomb. The whole sponge can be 

 compared to a honeycomb covered by a beehive, perforated by numerous aper- 

 tures, which are in direct communication with the cells inside. The osculaare 

 circular, and measure about 0-3 millim. in diameter. The oscular tubes are 

 0'4-l-5 millim. wide, and appear considerably constricted at their termination. 

 The oscula are confined to the walls of the vestibular spaces ; none are found 

 on the external surface. 



The sJceleton consists of main and connecting-fibres. The main fibres exteud 

 from a basal horny plate upwards ; distally they curve slightly outward, ramify 

 in a penicillate manner, and coalesce to form a reticulation. They are on an 

 average 0*3 millim. thick, and filled with a dense mass of large sand-grains. The 

 outer spongin coating measures only O'Ol millim. in thickness, and consequently 

 the surface of the fibres appears exceedingly uneven and knotty. These fibres 

 are joined by connecting-fibres 0*02 millim. thick, which are very simple, 

 mostly straight, perpendicular to the main fibres, and only slightly ramified. 

 The counecting-fibres are free from foreign bodies. With a high power a very 

 slender axial thread can be discerned in them, which swells to a little conic 

 granular extension at the point where the connecting-fibre joins the main fibre. 

 The cortex must be regarded as an integral part of the skeleton, as the 

 main fibres are coalesced with it. The sand-ffrains of the cortex measure 0"1 



