30 AXEL OHLIN, ARCTIC CRUSTACEA. 



This form, which is easily distingnishable hy the groove 

 011 the sixth segment of pleon. was lirst described by Kinahan 

 as a distinct species. It has proved impossible for me to get 

 the first paper in which it is named b}^ that anthor, so that 

 I am, consequently, not able to give an exact reference here. 

 I must, therefore. quote it after Kinahans låter and, as 

 I believe, more extensive memoir »On the Britannic Spe- 

 cies of Crangon and Galathea; with some Remarks on the 

 Horaologies of these Groups». 



There have been many dispiites as to the specific valne 

 of this form, and, in fact, the diiference between it and the 

 common Crangon vulgaris (Linné) does not seem to be very 

 great. But since Särs has published his remarkable observa- 

 tions on the development of these species, \ve cannot any 

 longer have any doubts as to their specific difFerence. The 

 great carcinologist traced the development of both species 

 which is, on the whole, more or less the same. He could, 

 liowever, \erj easily distingnish the species on whatever 

 stage by two very striking eharacteristics. In the larvas of 

 Cramion vulgaris the third segment of the pleon is provided 

 with a strong dorsal spine direeted at the rear which is quite 

 wanting in those of Crangon AUmanni. Besides that the 

 lateral spines on the fifth segment of pleon in the former 

 species are comparatively much larger than those in Cr. AU- 

 manni the larvas of which are, on the whole. larger and 

 more slender than those of Cr. vulgaris. 



This species seems to belong to the European side of the 

 North Atlantic. It was observed for the first time by Ki- 

 nahan at Dublin whence he established the species in 1850. 

 Låter on, it has been obtained at several places in the North 

 Sea, Skagerack, Kattegat, and the Sonnd, along the coast of 

 Norway where it occurs not infrequently as far east as to 

 the Mnrman Coast and the entrance to the White Sea. 

 During the Norwegian North Atlantic Expedition it was 

 also taken in the harbour of Reykiavik, Iceland. It lives 

 in moderate depths, 20—30 fathoms. Metzger obtained it 

 once from 69 fathoms,^ and my specimens were dredged 

 from 150 m. which. I think, are the greatest depths hitherto 



1 1. c. p. ^eo. 



