ON BOSMINID^, MACROTHEICIDJE, ETC. 405 



Discovered for the first time in Great Britain by Gf. S. B. in 

 East Belsay Lake, Northumberland, and subsequently in South 

 Shaws Loch, Selkirkshire. It is also known in Russia and 

 Norway. 



Genus. ANCHISTROPUS, G. 0. Sars. 



Carapace-valves united almost to the infero-posteal angle, and 

 having a peculiar angular projection rather before the middle of 

 the ventral margin ; head of great size, vaulted, and completely 

 covering, not only the anterior, but also the greater portion of 

 the posterior antennas. First feet in both sexes having a long, 

 cylindrical, falcate process denticulated on the edge, which is 

 very conspicuous, and projects beyond the valves. Eye and eye- 

 spot, excretory orifice, and general structure of abdomen, as in 

 Lynceus. 



Anchisteopus emaeginattjs, G. 0. Sars. PI. XIX, fig. 4 ; 

 and PL XX, fig. 4. 



1862. Anchistropus emarginatus, Gr. 0. Sars. Om de i Omeg. 

 af Christ, forekom. Clad. Andet Bidrag., p. 42. 



Carapace very tumid, somewhat semicircular, anterior, dorsal, 

 and ventral margins forming a continuous bold arch, valves united 

 almost to the infero-posteal angle, which is rounded off; ventral 

 margin on the posterior half nearly straight and ciliated ,• ante- 

 rior to this is a curious mucronate triangular projection, in front 

 of which the ventral side is terminated by a semicircular pro- 

 tuberance, the angle of the semicircle being towards the ventral 

 margin, and the arc towards the head. Head very large and 

 dome-shaped, concealed beneath which lie, not only the ante- 

 rior, but also the greater portion of the posterior antennas ; ros- 

 trum bent downwards, moderately long, and acute ; eye large ; 

 eye-spot nearer to the eye than to the extremity of the rostrum ; 

 posterior antennas very short, not extending beyond the rostrum. 

 Eirst feet terminating in both sexes in a conspicuously produced 

 cylindrical falcate process, bearing (five or six) denticulations on 

 the inside towards the distal extremity, and extending beyond 



