SPONGI'S. 87 



of a monaxonellid spicule from a tetractinellid form by subordination and fiiml 

 suppression of three of the rays. 



R.N. 223 (Station XLL, 12 miles off Galle, 100 fathoms). 



Geodia areolata, CARTER. 



1880, Geodia areolata, CARTER (4) ; 1888, Geodia areolata, SOU.AS (15). 



There are several specimens of this sponge in the collection. They are approximately 

 spherical in shape, and in form and colour closely resemble young specimens of 

 G. perarmata, but the largest sent to me is only 21 millims. in diameter. The surface 

 of the sponge is smooth and characteristically marked out into small stellate areas of 

 a pale yellow colour, separated from one another by a reticulation of chestnut-brown 

 pigment. This pattern, however, is not recognisable everywhere. Numerous small 

 apertures appear irregularly scattered over some parts of the surface, but with a 

 tendency towards grouping. These frequently occupy the centres of the pale stellate 

 areas, and they are often guarded by a fringe of convergent dermal oxea. They are 

 frequently covered over by a reticulate dermal membrane. They are the openings of 

 chones, which pierce the layer of sterrasters, but whether they are inhalant or 

 exhalant, or both, I have been unable to decide. 



The layer of sterrasters is about 0'46 millim. thick in the largest specimen. The 

 trisenes almost invariably extend their cladi beneath this layer, and do not pierce it 

 to reach the dermal membrane. The dermal oxea are abundant and arranged more 

 or less perpendicularly to the surface ; they extend from the outer surface of the layer 

 of sterrasters and project for a short distance beyond the dermal membrane. The 

 granular brown pigment cells, to which the sponge owes its characteristic colour, are 

 scattered in the ectosome outside the layer of sterrasters. 



The spiculation is as follows : 



(1.) Orthotriaenes ; with shaft about 2'37 millims. by 0'06 millim. 



(2.) Anatrisenes ; with very long and slender shaft and cladi about 0'054 millim. 

 long. 



(3.) Somal oxea; about 2'0 millims. by 0'029 millim. 



(4.) Cortical oxea ; about 0'2 millim. by O'OOS millim. 



(5.) Sterrasters; about 0'08 millim. in diameter, oval or nearly spherical. 



(6.) Somal chiasters or spherasters ; about 0'0083 millim. in diameter. 



(7.) Choanosomal oxyasters or spherasters ; mostly with few long and slender, 

 smooth rays; about 0'0165 millim. in total diameter. 



No typical protrioenes were seen, but only small plagiotriaenes, which may be young 

 forms of the large orthotritenes. 



In this case, as in that of G. perarmata, we can include the species in the genus 

 Geodia only by abandoning the restricted definition thereof given by SOLLAS. 



The species, as already indicated, is at first sight easily confounded with 

 G. perarmata. The specimens of the two were mixed together in the collection, and 



