364 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The specimen is roughly hemispherical and was probably attached 

 by the under surface, which is smooth and shows distinctly the radi- 

 ating skeletal bundles. Horizontal diameter about 30 mm. The pro- 

 jecting spicules of the upper and lateral surfaces have caught a quan- 

 tity of dirt. 



Small massive buds are present in considerable number at the sur- 

 face, impaled on the long spicules. Doubtless in correlation with 

 this condition the surface is made uneven by numerous small emi- 

 nences. 



The poriferous pits are all small, a typical one measuring 1.6 mm. 

 in diameter, 1.1 mm. in depth. They are abundantly scattered over 

 the upper and lateral surfaces, but owing to the dirt and projecting 

 spicules are inconspicuous. Some of the pits are narrow and cleft- 

 like, a shape which I take to be due to contraction. The membrane 

 lining the pits is smooth, and perforated with closely set pores. 

 Dendy regards some of the pits as afferent, others as efferent, and 

 this seems probable. Still I find a few simple apertures, 1-2 mm. 

 in diameter, scattered over the upper surface that seem to be oscula. 



The radiating skeletal bundles are made up of large oxeas together 

 with protriaenes and anatriaenes. The spicules projecting at the 

 surface are oxeas with intermingled protriaenes. 



The oxeas range down from 4 mm. by 50 tx, thus agreeing well 

 with the type. 



The protriaenes of the general surface have a rhabdome 4-6 mm. 

 long, 14 |x thick near the cladome, then tapering to a hair-like thick- 

 ness; clads 70-150 by 5-7 ix thick at the base. The spicules are 

 only fairly abundant, some projecting while the cladomes of others 

 lie in the ectosome. The protriaenes of the type are smaller, but it 

 may be that entire spicules were not measured. One suspects, per- 

 haps without warrant, that this was the case both for protriaenes and 

 anatriaenes, the rhabdomes of which are given as 460 jx or less 

 in length. 



Dendy does not describe the protriaenes of the poriferous pits, to 

 which I therefore give a few words. A pit is bounded all around 

 by radial skeletal bundles which include many protriaenes. These 

 lie chiefly on the side next the pit. Some pass out radially with the 

 oxeas, but many bend away from the bundle inclining themselves in 

 an obliquely radial direction toward the pit, the wall of which thus 

 becomes covered with the projecting cladomes of these spicules. 

 Such protriaenes are much smaller than those of the general surface, 

 the rhabdome varying down to a thickness of only 4 [x, the clads 

 to a length of 30 [x. 



The anatriaenes lie in the radial bundles, the cladomes in the 

 ectosome at different levels but not far apart. The more internal 

 spicules are evidently the younger, having shorter rays and more 



