151 



segments clothed at the end dorsally with a transverse row of still smaller dent- 

 icles, but having no lateral spinules. Caudal rami comparatively shorter than in 

 A. longiremis. Anterior antennae likewise somewhat shorter, scarcely exceeding 

 the length of the anterior division of the body, 5th articulation with a distinct 

 denticle in front. Length of apical spine of outer ramus in 2nd to 4th pairs of 

 legs scarcely exceeding that of the ramus. Last pair of legs with the terminal 

 joint produced to a strong claw-like spine minutely spinulose outside. 



Male resembling that of the preceding species, but having the caudal rami 

 comparatively shorter, and nearly as broad as they are long. Last pair of legs 

 very like those in the male of A. longiremis, though having the terminal joint of 

 right leg considerably narrower and that of left leg less expanded. 



Colour. Body in both sexes extremely pellucid and nearly colourless. 



Length of adult female 1.15 mm., of male 1.00 mm. 



Remarks. This form is so very like the preceding species that, without 

 a close examination, it may readily be confounded with it. This lias also actually 

 been done by Glaus, who described it as Diets longiremis Lilljeborg; and Brady 

 also seems to have confounded the 2 species. Dr. Giesbrecht, however, has pointed 

 out some minute differences between them, and as these differences are fairly 

 constant, they seem to justify the specific distinction of the two forms. The most 

 conspicuous distinctive characters are the different armature of the lateral lobes 

 of the last segment of the metasome and of the urosome, as also the compara- 

 tively shorter anterior antennae and caudal rami in the present species. The last 

 pair of legs in the female, moreover, conspicuously differ from those in A. lon- 

 giremis in the form of the terminal joint; and these legs in the male also exhibit 

 some slight differences, as shown by the figures here given. 



Occurrence. Off the south and west coasts of Norway this form is fully 

 as common as A. longiremis, in company with which species it is often found. 

 On the other hand, I have never met with it in any of the samples of plankton 

 from the Arctic Ocean. It accordingly seems to be a more southern form than 

 A. longiremis, and this assumption is also confirmed by what is at present known 

 of its foreign distribution. 



Distribution British Isles (Scott), Faroe Isles (Cleve), Heligoland (Glaus), 

 coast of France (Canu), Mediterranean (Giesbrecht), Black Sea (Karawajew), 

 Azores (Cleve), Atlantic Ocean between 36 and 61 N. Lat. (Giesbrecht); Gulf 

 of Guinea (Scott). 



