60 THE VOYAGE OF H.M.S. CHALLENGEE. 



finally, if either of the two alternative plans for choosing a single specific name were 

 adopted, it would be liable to result in considerable confusion between the species as 

 a whole and either of its constituent forms ; for example, Salpci fusiformis is now 

 generally used to indicate the aggregated form of its species, but it would, if the second 

 of the above plans were adopted, come to be the name for both the solitary and the 

 aggregated forms, — and it might in some cases be difficult to tell in what sense the 

 name was being used. 



In the case of a few species, where the solitary and aggregated forms were found 

 together, and their relationship was known when they were first described, only one 

 specific name was given, and in these cases, of course, there is no need for any change ; 

 but in the majority of the species, where the two generations have become well known 

 under distinct names, I believe it will lead to least confusion and trouble with 

 synonymy in the future if the double or compound names, as used in Traustedt's paper 

 and in the following pages, be systematically adopted.' 



The species in this genus are closely related, and are not readily separated into 

 natural groups. A discussion of their mutual relations, and a tabular synopsis of the 

 genus, will be found in Traustedt's recent paper. ^ 



The Challenger collection of Saljjw is very large, numbering between three and four 

 thousand specimens, but they are all referable to fourteen species, six of which are new 

 to science. 



Salpa costata-tilesii, Quoy and Gaimard — Cuvier (PI. IV. figs. 1-8). 



Salpa tilesii, Cuvier, Ann. du ]\Ius., torn. iv. p. 375, ISOi. 



Salpa costata, Quoy and Gaimard, Freycinet, Voyage, p. 504, 1824. 



Salpa costata-tilesii, Krohn, Ann. d. Sci. Nat. (Zool., st'r. 3), torn. vi. p. 114, 1846. 



Salpa costata-tilesii, Traustedt, loc. cit., p. 379, which see for further synonymy. 



All the specimens of this sf)ecies in the Challenger collection are more or less injured 

 or imperfect. They all belong to the solitary form Salpa costata, Quoy and Gaimard. 

 The localities are as follows : — 



(1.) June 23, 1874; Station 166, South Pacific, between Australia and New 

 Zealand; lat. 38° 50' 0" S., long. 169° 20' 0" E. ; surf. temp. 58°-5 ; one specimen (A). 



(2.) July 8, 1874; Station 168, off" the east coast of New Zealand; lat. 40°28'0"S., 

 long. 177° 43' 0" E. ; depth, 1100 fathoms; bottom temp. 37''-2, surf. temp. 57°-2 ; one 

 specimen (B). 



(3.) April 5, 1875 ; Station 230, North-West Pacific, to the south of Japan ; lat. 

 26° 29' 0" N., long. 137° 57' 0" E. ; surf temp. 68°-5 ; one specimen (C). 



(4.) October 18, 1875 ; South Pacific ; surface ; lat. 36° 0' 0" S., long. 132° 22' 0" "\V. ; 

 surf temp. 58°-5 ; one specimen (D). 



' Tills question of nomenclature is discussed more fully iu a paper published in Proc. Biol. Soc. Liverpool, vol. ii 

 p. 133, 1888. 



- Bidrag til Kundskab om Salperne, Vidensk. SiUk. Sb:, G Rskke, naturvid. og. math. Afd. ii. 8, p. 345. KjVben- 

 havn, 1885. 



