49 ] 



No. v.— AMPHIPODA HYPERIIDEA OF THE ' SEALARK ' EXPEDITION 



TO THE INDIAN OCEAN. 



By Alfred O. Walker, F.L.S., F.Z.S. 



Read 1st April, 1909. 



The following list of the Hyperiidea of the Percy Sladen ' Sealark ' expedition represents 

 the greater part of the Plankton Amphipoda. It consists of 28 genera and 35 species, 

 most of which are well-known pelagic forms widely distrihuted in tropical and 

 subtropical seas. The occurrence of Soma horealis, G. O. Sars, hitherto recorded only 

 from the Lofoten Islands, Norway, at a depth of 100-300 fras., is interesting. But how 

 easily these animals can adapt themselves to great changes of temperature may be 

 judged from the fact that of the 8 specimens taken 4 were from a depth of 25 fms., 

 with a surface-temp, of 82°, while the remaining 4 profess to have been taken at a depth 

 of 1200 f ms , where the temp, would probably be near 36°. As, however, this haul (0) 

 was not made with a closing-net, the depth at which they were taken is open to doubt. 

 The Wolfenden and Fowler closing-nets appear to have been used six times, but tubes 

 from only four of these contained Amphipods. These were as follows : — 



E (Wolfenden), 250* fras. One Hyperia bengalensis, ^ . 



I do. 500* „ One i/era/yjoAis young (Copepoda &c.). 



r (Fowler), 250-500 * fms. One Steyocephalns ylobosus, sp. n. (Previously described.) Two Vibilia 



gracilenta ; one V. robusta ; one Brachyscelus cruseulum. 

 s (Fowler), 350-0* fms. Four P hronimella elongata; one Paraphronima (/racilis ; one Hemityphis 



crustulatus. 



In addition to these a large ovigerous female of Platijsceliis armatus is said to have 

 been taken " off sounding-lead " at 209 fathoms. If the specimen was in the cavity of 

 the lead, it is almost certain that it was brought up from the bottom, an indication that 

 this species deposits its ova or young there. 



* These figures are taken from the tickets in the tubes. For localities, depths, &c., see Trans. Linn. Soc. ser. 2, 

 Zool. vol. xii. pp. 170-174. 



SECOND SERIES. — ZOOLOGY, VOL. XIII. 



