A NEW VARIETY OF THE HEXACTINELLID SPONGE, 

 RHABDOCALYPTUS DAWSONI (LAMBE) AND THE 

 SPECIES OF RHABDOCALYPTUS 



By H. V. Wilson and J. T. Penney 



Of the University of North Carolina, Chapel Hill, N. C. 



The sponge herein described was sent to us for identification by 

 the United States Bureau of Fisheries. It was " taken on a halibut 

 hook in 100 fathoms of water off Cape Spencer, Alaska." It is a 

 remarkably fine specimen, falling under Rhdbdocalyptus dawsoni 

 (Lambe). The differences from the type are for the most part 

 the usual quantitative ones which mark off the members of a widely 

 ranging species that live at some considerable distance from one 

 another. A more definite point of difference is exhibited by the 

 spicules lining the paragastric cavity and this makes it advisable 

 to classify the form as a (presumably geographical) variety. 



RHABDOCALYPTUS DAWSONI var. ALASCENSIS, new variety 



Diagnosis. — Variety marked off from the type by the autogastralia. 

 These are hexacts with tangential rays, 315/* to 385/x long, minutely 

 spinose; parenchymal ray usually shorter than tangential rays, 

 smooth or feebly spinose; free ray smooth or occasionally feebly 

 spinose, smoother and distinctly shorter than the other rays. 



Type-locality. — Off Cape Spencer Alaska. 



Holotype.—Q^i. No. 21382, U.S.N.M. 



Rhahdocalyptus {Bathydorus) dawsoni was established by L. M. 

 Lambe (1892, p. 73), for four specimens taken in 20-40 fathoms 

 off the coast of British Columbia. F. E. Schulze (1897, p. 37; 1899, 

 p. 54) after examining preparations made from one of Lambe's 

 specimens assigned the form to Rhabdocalyptus Schulze (Schulze 

 1887, p. 155), one of the genera with discoctasters (Lambe's dis- 

 cohexasters, 1892, pi. 6, fig. 2(S; the spicule often gives the appear- 

 ance of having only six instead of eight main rays). Schulze fur- 

 ther reports (1899, p. 55) on his study of three specimens and 

 some fragments of this species taken by the Alhaiross off the coast 



No. 2805.— Proceedings U. S. National Museum, Vol. 76, Art. 8 



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