204 



THE AMERICAN NATURALIST 



[Vol. XLII 



The Siboga dredged stalked crinoids at seventeen stations, in 

 all more than sixty specimens representing thirteen species and 

 two additional varieties. Three of these species are referred to 

 Bathycrinus, one to Rhizocrinus, two to Isocrinus, and the re- 

 mainder to Metacrinus, while the species of Rhizocrinus dredged 

 by the Valdivia off Somaliland and recorded by Chun in 1900 is 

 included in the report, and figured under the name of R. chuni. 



The species referred to the first two genera are of very excep- 

 tional interest, apart from the fact that neither genus has been 

 recorded from the East Indian region; while the Rhizocrinus 

 (B. weberi n. sp.) is related to B. rawsonii of the tropical At- 

 lantic, the three Bathycrinus are in their characters quite unlike 

 anything previously known ; in the first place, they are all very 

 small, one species, B. poculum, being only 8 mm. in total length, 

 while none of the others exceeds 35 mm. ; but, most remarkable 

 of all, they unite the characters of Bathycrinus and Rhizocrinus 

 so completely as to leave scarcely any grounds for considering 

 them as distinct genera. This discovery was not news to the 

 present reviewer; for the day after the receipt of Dr. Doderlein's 

 work, his own description of two intermediate species, Bathy- 

 crinus equatorialis and B. caribbeus was published. Rhizocrinus 

 (including, as we now apparently must, Bathycrinus) contains 

 at the present writing fifteen described species, of which nine 

 have been made known during the past year, and there are sev- 

 eral additional species now in press; it is very evident that our 

 knowledge of even this comparatively old genus is still extremely 

 rudimentary. Dr. Doderlein's interesting remarks on the shed- 

 ding of the arms in Rhizocrinus— Bathycrinus I shall consider 

 in detail later. 



Isocrinus naresianus, first found by the Challenger, was redis- 

 covered by the Siboga off the northern end of Celebes, having 

 been previously known only from the Kermadec and the Meangis 

 Islands, and from Fiji, and a new species, 7. sibogm, was dis- 

 covered near Timor. This last belongs to the group of the genus 

 in which the costals and division scries consist of two joints, 

 bound by syzygy, including such species as 7. wyville-thomsoni, 

 I. parrm (of Guerin 1835 = 1. miilleri of Oersted 1856 of which 

 7. maclearanus is merely a variety) and 7. alternicirrus, to the 

 last of which 7. sibogai is most nearly related, though it possesses 

 the normal arrangement of the cirri. The form maclearanus, by 

 the way, did not come from the southwest Atlantic as stated 



