238 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



of unicellular algae. In other respects they were much like the type specimen. 

 The consistency was cartilaginous, though spicules could be felt by the 

 fingertips. 



The surface of this species is in places smooth and in places hispid. Some 

 specimens are smooth nearly all over, but Specimen No. M. 386 was hispid 

 nearly all over. The regions not covered by projecting spicules are shiny 

 smooth. The pores are extremely contractile, probably very numerous and 

 small. Oscules are also very difficult to make out, but in the type specimen 

 there were a few apertures, 2 to 10 cm in diameter, quite readily observed. 

 On the other hand, it is by no means certain that these are oscules, because 

 they may be accidental or fortuitous punctures. 



The ectosome is typically corticate, about 0.7 mm thick. The inner 

 boundary of this cortex is sharply marked off from the endosome, but it is 

 uneven. It is characterized by projections about 20 fx in diameter, 30 p. long, 

 and about 40 p apart, summit to summit. These projections interdigitate with 

 similar ones from the endosome. The endosome itself is vaguely radiate but 

 is rather crumb-of-bread, or microcavernous, with many spicules in confusion. 

 The plagiotriaenes, however, are quite distinctly radiate in placement with 

 their cladomes immediately below the cortex and parallel to it. 



The skeleton comprises first oxeas of great size variation, ranging from 

 as small as only 4 p by 240 p (which is rare) to as large as 40 p. by several 

 thousand /i (which is more common). Very many are between 20 p by 1000 /x 

 and 40 p. by 2000 fx. There are plagiotriaenes, with clads up to as much as 

 40 ix by 170 [x and rhabds 40 [x by several thousand jx long. Protriaenes are 

 probably always present, but they are rare and were found only in Specimens 

 No. M. 231, M. 165, and M. 157. These have clads about 8 ^ by 50 /i and 

 rhabds 8 p by 1000 p, more or less. The anatriaenes are more consistently 

 present. They have clads about 15 jx by 150 fx or less and rhabds 15 p. by 

 1500 jx, more or less. The most characteristic spiculation is that of the micro- 

 scleres. These are straight rhabds, about 10 p to 13 fx long and 1 /x to 1.5 p in 

 diameter. They are covered all over with very minute spines. These spicules, 

 instead of having pointed terminations, or even rounded ones (as is true of 

 strongyles), come to extremely sharply cut-off or flat ends. This is re- 

 markable. 



The genus Hezekia was established by de Laubenfels, 1934, page 4, for 

 the one species H. demera, from the West Indies. The present species, 

 walkeri, differs from the earlier one chiefly in the shape of the microrhabds. 

 Those of demera were sharply pointed at the end, and smaller, being only 

 1 p. by 5 ix to 1 /x by 8 p. The coloration of demera was very dull, showing 

 none of the distinctive hues exhibited by zvalkeri. 



The specific name is given in honor of the late Mr. H. D. Walker. 



