VOL. XII, PP. 41-51 MARCH 24, 1898 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



THE ARCTURED^ IN THE U. S. NATIONAL MUSEUM.* 



BY JAMES E. BENEDICT, 



Assistant Curator, Division of Marine Invertebrates, U. S. National Museum. 



When Mr. Beddard wrote the Report on the Isopoda collected 

 by the 'Challenger' in 1886, but five species of Arcturus had 

 been recognized. He added thirteen. Since his report no addi 

 tional species have been described. In this paper five species 

 taken by the 'Albatross ' and one by the Point Barrow Expedi 

 tion are described as new and a subspecies is raised to specific 

 rank. 



The structure and habits of the Arcturidse are such that deep- 

 water species are likely to occupy only restricted areas. The 

 young are few in a brood and are cared for by the parent until 

 well able to care for themselves, clinging to the mother's antennae 

 until ready to undertake a more independent existence, perhaps 

 on the very object on which the mother is foraging for herself 

 and brood. With habits of this kind the chances of a wide dis 

 tribution for any one species must be very much less than is the 

 case where free-swimming young are produced in large numbers. 



The character of the marsupium of Arcturus is sufficient to 

 separate this genus from A.stacilla. The dactyls of some species 

 of Arcturus are biungulate as in Astacilla. 



Two species of Astacilla are described as new, one from the 

 Straits of Magellan and a blind species from deep water (1,825 

 fathoms) off Martha's Vineyard. The finding of a blind Astacilla 

 in deep water is a matter of no little interest. Mr. Beddard 



* Published by permission of the Secretary of the Smithsonian Institu 

 tion. 



10 BIOL Soc. WASH., VOL. XII, 1898 (41) 



