176 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



The ectosome is set off by extensive subdermal cavities. The dermal 

 membrane is protoplasmic and only about 5 tt thick. It is chiefly aspiculous 

 but does contain some strongyles arranged tangentally. The axial specializa- 

 tion makes up as much as 80 per cent of each projection but forms only a 

 much smaller per cent of the main body of the sponge. In it, the spicules 

 are mostly longitudinal but are crowded. Around this axis, as already noted, 

 there is a zone of extensive subdermal space liberally interspersed with fasci- 

 cular columns at right angles to the axial specialization. These serve to sup- 

 port the roof, which is the above-mentioned dermal membrane. From ceil- 

 ing to floor this subdermal space measures slightly over 300 p. 



The skeleton contains some spongin, but it is pale and inconspicuous. 

 The principal spicules present are strongyles, 6 it by 330 it. In boiled-out 

 preparations a considerable number of styles also are found. These are 

 thinner, only 3 tt by 330 fi, and there are also quite a number of raphides 1 tt 

 by 300 tt. It is possible that these are merely juvenile forms of the other 

 spicules. In studies of sections, the skeleton in all places consists principally 

 of strongyles. The dermal spicules seem to be exclusively strongyles. The 

 fascicular columns of the ectosomal region are all, or nearly all, strongyles. 

 Certainly, the bulk of the spicules in the solid mass which makes up the axis 

 specialization are strongyles. It cannot be stated with certainty that there is 

 any particular localization of the styles. 



The genetic allocation of this species is quite difficult ; one is tempted to 

 erect a new genus for it. Externally, it resembles the genus Ommatosia, but 

 that genus has no styles at all. In almost every way it is close to the genus 

 Phakellia, but in Phakellia the structures which are perpendicular to the axial 

 specialization are made up altogether of styles, the strongyles being confined 

 to the axis. Most of those species which have been referred to Axinosia 

 emphasize styles and perhaps should not be placed in that genus. Its type 

 is the sponge originally described as Axinella symbiotica by Whitelegge, 1907, 

 page 508, from Australia. This is probably the closest other relative of xutha, 

 from which it differs chiefly in having spicules much larger, up to 20 it by 

 300 it, and by having dark rather than pale spongin. Also its surface was 

 not so elaborate. 



The specific name xutha is derived from a Greek word which is thought 

 to mean "orange color." 



GENUS PHYCOPSIS Carter 

 Phycopsis terpnis, new 



Text Figure No. 116 



This species is here represented by the following: 

 U.S.N.M. No. 23061, My No. M. 441, here designated as type, collected 

 August 3, 1949, by diver from a reef in the lagoon near the shore in 



