56 PEOCEEDINGS OP THE NATIONAL MUSEUM vol.81 



specimen, the narrow-meshed terminal sieve plate is united all 

 around to the thinner body wall and is not separated by several open- 

 ings of new additional zooecial tubes, as in Aphrocallistes hocagei P. 

 Wright. 



APHROCALLISTES YATSUI, new species 

 PlATE 4, FiGUKES 2, 3 



A nearly complete specimen (holotype, U.S.N.M. No. 22108) of 

 A. yatsui was collected from Station 4781 (near the western extrem- 

 ity of the Aleutian Islands at 482 fathoms). The body shows a some- 

 what dorsoventrally compressed, cuplike form, gradually narrowed 

 toward the stalklike basal regions, and expanded toward the nearly 

 truncated oscular edges. The surface of the sponge is very porous, 

 owing to the great numbers of large and small afferent canals, the 

 outer ends of which are generally rounded and vary in size up to 

 1 mm in diameter. Nearly all of them are large enough to be noted 

 macroscopically. The surface has a very homogeneous appearance. 



It is generally difficult to trace the distinction between a dermal 

 surface and a gastral surface in this sponge. On the gastral surface 

 the larger and smaller efferent canals make their appearance, ar- 

 ranged somewhat regularly and much more visible than on the dermal 

 surface. The outer edges of the efferent canals are usually raised to 

 a slight degree by the thickening of the gastral surface. 



Spiculation. — The arrangement of the constituent beams of the 

 dictyonal framework has a certain regularity. Beams directed radi- 

 ally to the surface of the sponge may be distinguished. Between 

 these lie the connectives, which are frequently transverse, thus giving 

 rise to rectangular meshes. The superficial ends of the radial beams 

 form tapering spines of varying lengths, sometimes very short, fre- 

 quently long, often slightly irregular, and as a rule thickly covered 

 with microtubercles. The beams in general are sparsely covered with 

 similar tubercles. Usually they are 80/x thick. 



Slender, sharp, tuberculated spines generally project from the 

 nodes of the skeletal reticulum, on the free surfaces and edges of the 

 plate. Some of the very delicate connecting bars that extend be- 

 tween the adjoining skeletal plates give the impression of having 

 arisen through the fusion of such spines. 



The dermalia are exclusively hexactinic pinules, so far as those 

 of the body proper is concerned. The pinular ray as a whole 

 is nearly spindle shaped, 160/i, to 200/* long and 30/* to 50ja broad 

 in the middle, which is about the broadest part. In this part, the 

 obliquely upwardly directed, conical spines are closely distributed. 

 The rhachis is smooth for a short distance at the base, which is 

 about 12/i thick ; its conically pointed outer end forms the tip of the 

 pinular ray. The remaining five rays are somewhat slender, and 



