CRUSTACEA MALACOSTRACA. 83 



were used, whereas those taken with 100 meters wire out are but small and far from mature. The 

 structure of ^>". arcticus, the good state of preservation of the specimens taken by the "Ingolf" and 

 the observations mentioned of the "Thor" show clearly that the species is not a bottom-form, but 

 lives pelagically; large to very large specimens are however never taken near the surface, and the 

 largest are not met with, at least as a rule, above a depth of about 250 fm. and they descend probably 

 a good deal lower. — The specimen taken by the "Ingolf at St. 140 has certainly been carried by the 

 Gulf Stream into the Norwegian Sea and has been taken in the warmer layers, as the species un- 

 doubtedly does not live at the great depths with temperatures below o° in the cold area. 



Remarks. In my two papers on Sergestcs mentioned above, I have dealt with the characteristics 

 of this species, its distribution, the list of synonyms and likewise some of its larval stages, of which 

 one has been described as Sergestcs Rinkii Kr. The largest "Ingolf" specimen came from St. 9 and 

 measures 55 mm. 



79. Sergestes robustus S. I. Smith. 



! 1882. Sergestes robustus S. I. Smith, Bull. Mus. Comp. Zool., Vol. X, No. 1, p. 97, PI. XVI, figs. 5— S b. 

 1886. S. I. Smith, Rep. Coram. Fish & Fisher, for 1885, p. 697, PI. XX, fig. 6. 



I 9°3- — — H. J. Hansen, Ann. and Mag. Nat. Hist, Ser. 7, Vol. XI, p. 480, figs. 6 & 7. 



— biennis H. J. Hansen, Ann. and Mag. Nat. Hist., Ser. 7, Vol. XI, p. 479, figs. 1 — 5 (barely 



half-grown specimen). 



Occurrence. The "Ingolf" has not taken this species, but I have seen specimens from the 

 following place. 



South-West of the Faroes: 6i°o8'N. L,., 9°46'W. L., 450 fm., 3 specimens taken by the "Michael 

 Sars" ('-J/g 1902) and belonging to the Bergen Museum. 



Distribution. It has been taken at 59°49' NX., g°46'W. L. by the "Thor", at ^Z°\^ N. L., 12 27' W.L. 

 (Hansen), in the Mediterranean (Hansen) and at a number of places off the east coast of North America 

 between 4i I / 3 ° and 34 28' N. L., in depths from 372 to 2574 fm. In the "Summary of the Deep-Sea 

 Zoological Work of the Royal Indian Marine Survey Ship "Investigator" from 1884 to 1897", 1899, 

 p. 30, Alcock writes concerning this species: "Off coasts of South-India and Ceylon 200—902 fathoms 

 (common)"; but it is somewhat remarkable that he does not include it in his "Descriptive Catalogue 

 of the Indian Deep-Sea Crust. Dec, Mac. and Anomura, 1901". 



Remarks. The largest specimen from the locality mentioned was 60 mm. long when scarcely 

 fully extended. The specimens agree very well with a specimen determined by Smith received from 

 the U. S. Nat. Museum. The specimen from the "Thor" is 90 mm. long. 



It appears from the list of synonyms, that I now consider the S. iucnuis founded by me in 



1903 on a single not quite half-grown specimen as a young stage of X robustus shortly after the 



larval period. I have come to this result from a study of a considerable material from the Monaco 



Museum, from E. Holt, and from the "Travailleur" and "Talisman". The reasons for my considering 



in 1903 the differences between an adult specimen of S. robustus and the specimen described as 



51 inermis to be specific differences, arose in the first place from the complete lack of transitional 



stages, and in the second from the fact that our Museum possesses some plump specimens, some of 



11* 



