112 PROCEEDINGS OF THE NATIONAL, MUSEUM. vol.81 



the prostal pleuralia have increased in number. The latter are 

 abundant over the entire stock. 



Spiculation. — The diactinic prostal marginalia are very long, meas- 

 uring 15 mm to 20 mm, and are inserted over half or more of the 

 entire length. They measure 132/a to 176/x in diameter in the middle 

 and are gradually tapered at both ends. They are smooth on the 

 surface, except at both ends, which are usually minutely tubercu- 

 lated, although occasionally not tuberculated in the larger specimen. 

 Prostal basalia have a shape somewhat different from the other pros- 

 tal marginalia and prostal pleuralia. They measure 0.132 mm to 

 4.79 mm in length and 22)U, diameter in the middle. They are slightly 

 narrowed proximally, but become broad distally, usually forming a 

 distinct knob-shaped swelling. Both ends are strongly tuberculated. 



The discoctaster is rare. The microdiscohexaster may be lacking. 



RHABDOCALYPTUS ITNGUICULATUS Ijima 



Rhabdocalijptus unguwuJatus Ijima, Journ. Coll. Sci. Imp. Univ. Tokyo, vol. 18, 

 art. 7, pp. 268^276, pi. 21, figs. 1-12, 1904. 



This species is represented by two specimens obtained from a depth 

 of 482 fathoms near the western extremity of the Aleutian Islands 

 (Station 4781). It has hitherto been recorded from the Sagami Sea 

 in Japan, and this is the first time it has been collected so far north. 

 The smaller specimen (A) differs a little from R. unguiculatus^ but 

 I am nevertheless inclined to identify it with that species. It is 

 almost completely preserved, lacking only the basal parts of the 

 stock. It is vaselike in form, 125 mm in height and 50 mm broad 

 in the middle. The thickness of the wall at this point is 6 mm to 

 7 mm. The osculum is smaller than that of the type species, meas- 

 uring 11 mm in size. The gastral latticework, however, is discontin- 

 uous. Its meshes are not vaulted, and, being filled with the choano- 

 some, are not visible to the eye. 



Spicylation of specimen A. — The discoctasters have much smaller 

 dimensions, in diameter measuring 108/i to 140;li. I have even seen 

 a few of them outside of the dermal layer. One point of difference 

 from the type specimens is that they probably occur in two very 

 slightly differing sizes, the one chiefly in the hypodermal and hypo- 

 gastral layers and the other in the parenchymal space. The hypo- 

 dermal and hypogastral discoctasters are slightly larger than tliQ 

 latter, measuring 135/^, to 140/x in diameter. The central node arising 

 from the principals is very prominent. The parenchymal discoc- 

 tasters measure 108/x to 112/x in diameter and infrequently the central 

 node is indistinct. In general, the terminals of the oxyhexaster are 

 much more fragile and slightly more wavy than those of the type 

 specimens. 



