34 THE VOYAGE OF H.M.S. CHALLENGER. 



I have little doubt that both Schmeltz aud Miers are quite right in regarding these 

 two species as identical ; it is impossible, either from the description or the figures con- 

 tained in the memoir of Audouin and Milne-Edwards, to select any characters by which 

 the two species Serolis fahricii and Serolis orhigniana can be definitely distinguished ; 

 such diff'erences as there are appear to me to arise from the fact that the two " species " 

 are in reality merely the males and females of the same species, Serolis fahricii. 



With regard to the name I have followed Miers and written Serolis paradoosa ; this 

 name evidently has the priority. 



A number of specimens of Serolis jJctradoxa were dredged by the Challenger at the 

 Falkland Islands, and this, together with the adjacent shores of Patagonia, is the only 

 locality which the species is known with certainty to inhabit. According to Leach, Serolis 

 paradoxa extends to the west coast of Africa ; he makes the following remarks about its 

 distribution (loc. cit., p. 340) — " I have only seen two specimens ; one is in the collection 

 of Banks and comes from Tierra del Fuego ; the other is in my possession and was given 

 me by Dufresne, who tells me that he received it from Senegal." The specimen from 

 Senegal is now in the British Museum, and is labelled in the handwriting of Leach. The 

 British Museum contains another specimen of Serolis paradoxa which is labelled " New 

 Zealand," but I believe that in this case, as in that of Serolis schythei to be mentioned 

 later, the locality is not thoroughly authenticated. Miers includes Serolis paradoxa in 

 his list of New Zealand Crustacea apparently on the authority of this same specimen. 



The males and females of this species are not distinguishable by any well marked 

 difference of size ; the males are, however, a little broader proportionately, as is shown by 

 the following measurements taken from two of the largest specimens obtained by the 

 Challenger. 



Male, ....... 



Female, ...... 



The form of the abdominal sterna differs in the two sexes; in the male the outline is 

 somewhat crescentic, the posterior margin being curved and the anterior margin almost 

 straight ; in the female each of these segments bears a median spine upon the posterior 

 margin directed backwards and closely overlapping the succeeding segment. In this 

 character Serolis paradoxa agrees with Serolis schythei, but the spines in the females 

 are longer than in that species. The above measurements do not express the greatest 

 size to which this species attains ; there are several specimens in the British Museum 

 somewhat larger, and White states^ that individuals have been known to reach the 

 great length of 6 inches ! This last statement, however, requires confirmation. 



Serolis paradoxa is, as Grube remarks,^ more nearly allied to Serolis schythei than to 



1 Wiite, Description of New Species of Insects and other Annulosa, Ann. and Mag. Nat. Hist., 1843, vol. xii. p. 3GG. 



2 Loc. cit., p. 225. 



