THE SPONGES OF THE WEST-CENTRAL PACIFIC 187 



The surface is even and punctiform. Some of the openings, which may 

 be as large as 180 /x by 280 fx, perhaps are oscules ; and others, which range 

 from 15 ju, to 30 ju, in diameter, are the true pores. These are sometimes but 

 not always aggregated into clusters, as much as 200 /x in diameter. In some 

 cases the cluster looks like a large pore covered by a sieve. 



The ectosome is much more densely fleshy than the endosome, but the 

 subdermal cavities are only moderately noticeable. The endosome is primarily 

 colloidal in structure, but there are rather conspicuous flagellate chambers, 

 30 (i to 35 /x in diameter. 



The skeleton consists of spicules in confusion, but all are exceedingly 

 small. The largest are microxeas, 1.2 [x by 80 [x to 1 /x by 110 /a. There are also 

 exceedingly abundant trichodragmas, the individual raphides of which are 

 0.3 ix by 80 fx to 0.4 fx by 50 p. 



The distinctive features of the species are included in those of the genus, 

 this being the first species of the genus. 



The name here selected refers to the family Milne, various individuals of 

 which lived in the region studied and contributed materially to the making 

 of the collection upon which this treatise is based. Special attention is called 

 to two outstandingly capable natives of the Marshall Islands. They are 

 cousins, each named James Milne. 



FAMILY HYMENIACIDONIDAE de Laubenfels 



GENUS HYMENIACIDON Bowerbank 



Hymeniacidon aldis, new 



Text Figure No. 125 



This species is here represented by the following : 

 U.S.N.M. No. 22940, My No. M. 310, here designated as type, collected June 

 20, 1949, by diver at Ailing-lap-lap Atoll from the channel near Bikajela 

 Islet. The depth was 10' meters, and the substrate was dead coral. 



This is an irregularly columnar specimen, 1.3 cm in diameter and 2.8 cm 

 high. 



The exterior and interior color in life was bright orange, and the con- 

 sistency softly spongy. 



The surface is microconulose and lipostomous. 



The ectosome consists only of a very thin fleshy dermis. The endosome 

 is primarily protoplasmic but contains a jumble of spicules in confusion, 

 showing a vague plumose arrangement. 



The skeleton consists entirely of smooth thick styles, often somewhat 

 bent. The sizes range from about 14 fx by 500 fx to 20 fx by 500 [x. 



This is a dubious and puzzling specimen. The generic allocation is far 

 from certain. Consideration must be paid to the possibility that it is an ab- 



