184 



exceeding the length of the body, peduncles of both clothed, on their opposite 

 edges, with numerous transverse rows of short sensitive hairs, flagella extremely 

 slender and nearly naked. Anterior gnathopoda a little stronger than the 

 posterior ones, with the propodos oblong oval, and considerably shorter than 

 the carpus ; that of the posterior ones much narrower, and slightly tapering 

 distally. Anterior pairs of pereiopoda with the propodal joint rather narrow, 

 and considerably longer than the carpal joint, dactylus slender, and somewhat 

 exceeding the length of the former. The 2 succeeding pairs with the basal 

 joint much less broad than long, and having the anterior edge evenly curved, 

 and fringed with ciliated setae, carpal joint with about transverse rows of 

 spinules on its outer side, dactylus comparatively short. Last pair of pereio- 

 poda with the posterior expansion of the basal joint reaching considerably 

 beyond the meral joint and nearly transversely truncated at the tip, inferior 

 and anterior edges defined by an obtuse angle, carpal joint fully as long as 

 the 2 preceding joints combined, and having a row of about 9 slender spines 

 along the anterior edge, propodal joint a little shorter. Last pair of nropoda 

 with the rami sharply pointed at the tip, their opposite edges finely serrated, 

 and having near the base a projecting corner, inner ramns with 8 denticles 

 on the inner edge. Telson rounded, nearly as long as it is broad, witli a few 

 marginal hairs, and two somewhat longer bristles at the tip, incision very 

 short, rounded at the bottom, Body whitish, pellucid, with faint orange- 

 coloured shadows, frontal part of the cephalon densely mottled with dark 

 violet. Length of adult female 15 mm, of male somewhat less. 



Remarks. - This form was first recorded by Kroyer as an Ampelisca, 

 and was figured in the well known work of Gaimard, as Ampdisca Gaimardii 

 In the year 1870 Boeck, however, justly separated it from that genus, and 

 established the genus J3yl)lis for its reception. It may thus be regarded as 

 the type of the present genus. The Bylilis serrata of Smith, of which species 

 I have had a specimen for examination, kindly sent to our Museum, from that 

 author, is very nearly allied to the Kroyerian form, but apparently distinct. 



Occurrence. - The species is a genuine arctic form, occurring rather 

 abundantly everywhere off the coast of Fimnark, in moderate depths. It also 

 however, extends southwards along the whole west coast of Norwaj^, and is 

 even occasionally met witli off the south coast, to the Christianiafjord. 



Distribution. Arctic Ocean widely distributed : Greenland, Labrador, 

 Iceland, Spitsbergen, the Murman coast, the Kara Sea, the Siberian Polar 

 Sea; Kattegat (Meinert), Bohuslan (Bruzelius) *). 



*) The statement, of its occurrence also in the Mediterranean off Naples (Costa), and in 

 the Adriatic (Heller;, seems to me very questionable, and may most probably result 

 from its being confounded with some nearly allied species. 



