268 ERYLUS OX VASTER. 



the Pacific species, not in the "Albatross" collection, will be found in the first 

 part of this monograph. 



Tlic family Erylidae thus comprises the single genus Erj-lus. 



ERYLUS (!n\Y. 



With uniporal afTcrents and uiiiporal efferents or larger oscules. Without 

 ana- or protriaenes. 



There are in the "Albatross" collection t\venty-t\V(j specimens which l)elong 

 to four species, one of which is divided into three varieties. All tlie species and 

 varieties are new. 



Erylus oxyaster. sp. nov. 

 Plate 3, figs. 29-3.T; Plate 4, figs. 1-43. 



I establish this species for a specimen obtained in the Galapagos Islands. 

 Its asters are oxyasters and to this the name refers. 



The single, somewhat fragmentary specimen (Plate 4, fig. 24) is 30 mm. 

 in maximum diameter and consists of two rounded lobose parts, one of which 

 is broad cushion shaped, the other sleiuler, thgitate. The surface is smooth 

 and bears numerous small afferent pores. These are quite uniformly dis- 

 tributed and 0.7-1 nmi. apart. On the summit of the broader of the two lobes 

 an irregularly circular oscule, 1.8 mm. in diameter, is situated. 



The colour of the surface of the sponge (in spirit) is brown. A small part 

 of it, which was probably sheltered from tlic liglit. is much lifiliter tlian the rest. 

 The interior is light greenish yellow. 



The superficial part of the body is (liffcrentiatcd to fmin a cortex 4.')0-0r)0 /'. 

 thick. This is composed of two layers, an outer layer, 75-120 /'. thick, occupied 

 by microrhabds, and an inner layer 360-560 /t thick, occupied l)y aspida.sters. 



Canal-system. Many of the afferent pores appear to be quite closed. The 

 open ones (Plate 4, fig. 25) are circular and surrounded by fine sphincter-mem- 

 bi-anes in which numerous more or less radially disposed microrhabds are 

 situated. These pores are 30-60 fi wide. They lead into radial canals which 

 traverse the cortex and open out into subcortical cavities the radial diameters 

 of which are usually greater than the paratangential. 



The skeleton consists of regular rhabd megascleres, irregular tlerivates of 

 these, microrhabds, teloclades, aspidasters, and ox}'a,sters. The rhabd mega- 

 scleres are for the most part amphioxes, but a few styles have also been 

 observed. These rhabds and their irregular dcrivates form bundles which 



