6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.76 



(mummified) near the gastral surface that individual cells and in- 

 tercellular connections are still plainly recognizable and the spicules 

 should be visible, one would think, if actually present. Schulze 

 (1897, p. 37; 1899, p. 55) observed these spicules both in the Alba- 

 tross specimens and in preparations made from one of Lambe's 

 specimens. He records them as numerous; diameter 20/i, to 35/^,; 

 terminal rays 8-12, longer than the j)rincipals, delicate and knobbed. 

 He notes (1904, p. 35) that these very small and delicate spicules 

 are rare and difficult to observe in some individuals of many 

 Rhabdocalyptus species. Ijima (1897, p. 45) thinks they are prob- 

 ably never absent, although rare in some species. Schulze (1904, p. 

 36) regards their apparent absence, as in the cases of R. lophodigi- 

 tatus {plumodigitatus) Kirkpatrick and R. australis Topsent, as 

 having no significance for classification. 



Ijima in his splendid report (arranged for publication by Yai- 

 chiro Okada) on the Siboga hexactinellida lists (1927, p. 377) the 

 known species of RhabdocoLyptus^ 13 in number. The following 

 brief diagnoses of the species other than R. dawsoni will serve to in- 

 dicate the persistent lines of past variation within this group. 



R. tener F. E. Schulze (1899, p. 57), coast of California. Auto- 

 dermalia, pentacts and hexacts. Autogastralia larger than auto- 

 dermalia, hexacts with free ray longer and more spinose than the 

 others. Oxyhexasters (varying, as in the other species of the genus, 

 to the hexactine shape, Ijima 1897, p. 45) with spheroidal central 

 thickening; terminal rays exceedingly slender. Discoctasters 80/* 

 to 100/x, diameter; the nodal protuberances, representing the six 

 primary rays of the primitive hexact, unusually large and con- 

 spicuous. Microdiscohexasters not observed. 



R. nodulosus F. E. Schulze (1899, p. 58), coast of California. 

 Autodermalia, stauracts and pentacts. Autogastralia, strong oxyhex- 

 acts, free ray usually longer and more spinose than the others. 

 Oxyhexasters with spheroidal central thickening. Discoctasters 

 large, 240/a to 300/a diameter. 



R. asper F. E. Schulze (1899, p. 60), coast of California. Autoder- 

 malia, pentacts and stauracts. Autogastralia, hexacts and pentacts. 

 Prostal hypodermal pentacts all large; some with tangential rays 

 that measure as much as 1-2 cm. in length and are smooth or with 

 only a rough shagreenlike surface. Oxyhexasters 140/t to 160/j, diam- 

 eter. Discoctasters 150/i to 200/* diameter. 



R. mirahilk F. E. Schulze (1899, p. 61) , coast of Alaska. Autoder- 

 malia for the most part small diacts; some pentacts and stauracts. 

 Autogastralia, oxyhexacts; free ray 500/t long and spinose; other 

 rays 200/* long, roughened. Oxyhexasters about 120/* diameter. 



