268 



ERYLUS OXYASTER 



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

 part of this monograph. 



The family Erylidae thus comprises the single genus Erylus. 



With uniporal afferents and uniporal efferents or larger oscules. Without 

 ana- or protriaenes. 



There are in the "Albatross" collection twenty-two specimens which belong 

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

 varieties are new. 



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

 Its asters are oxy asters 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 slender, digitate. The surface is smooth 

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

 tributed and 0.7 1 nun. 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 probal^ly sheltered from the light, is much lighter than the rest. 

 The interior is light greenish yellow. 



The superficial part of the body is differentiated to form a cortex 450-650 /i 

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

 by microrhabds, and an inner layer 360-560 n thick, occupied by aspidasters. 



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

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

 branes in which numerous more or less radially disposed microrhabds are 

 situated. These pores are 30-60 // 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 derivates of 

 these, microrhabds, tcloclades, aspidasters, and oxyasters. The rhabd mega- 

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

 observed. These rhabds and their irregular derivates form bundles which 



ERYLUS Gray. 



Plate 



.3, figs. 29-3.5; Plate 4, fig.s. 1-13. 



