128 G. o. SARS. CRUSTACEA. [NORW. POL. EXP. 



sinuated in the middle, dorsal straight, with a slight depression in the middle, 

 and joining the hind margin at an obtuse angle: seen ventrally, regularly 

 oblong ovate, greatest width somewhat exceeding Vs of the length, and occur- 

 ring in the middle, anterior extremity narrowly subtruncate, posterior acute. 

 Shell of male comparatively narrower than that of female, sub-cuneate, with the 

 posterior extremity (seen laterally) obliquely truncated, and the ventral margin 

 more distinctly sinuated. Valves thin and pellucid, sculptured with 2 sets of 

 curved striae crossing each other, and producing a close, but not very con- 

 spicuous reticulation, postero-dorsal corner armed with 3 or 4 small blunt 

 teeth, somewhat increasing in size posteriorly. Extremity of frontal tentacle 

 in both sexes club-shaped, hispid, but in male thicker and more sharply 

 marked off at the base. Antennulae in male with the 2 sensory appendages 

 of about equal size, anterior apical seta much longer than the other 2, and 

 having the median part somewhat thickened, and armed with numerous recurved 

 denticles, its distal 3rd part abruptly bent downwards. Claw of accessory 

 ramus of male antennae much larger on the right than on the left side. 

 Basal joint of mandibular palp about the length of the 2 succeeding joints 

 combined. Caudal lamellae each with 8 slender claws rapidly increasing 

 in length anteriorly, the last, as usual, somewhat remote from the others, 

 all being finely denticulate along the posterior edge. Length of adult female 

 3'50 mm., of male 3'20 mm. 



Remarks. This form is very closely allied to one of the Norwegian 

 species recorded by the present author under the name of C. borealis. It is, 

 however, of larger size, and differs moreover, in the less strongly marked 

 sculpture of the shell, as also somewhat in the form of the latter. On a 

 closer comparison, some minor differences may also be found to exist in 

 the structure of the several appendages. 



Description of the Female. 



The average length of the shell in fully adult specimens is 3'50 mm., and 

 Messrs. Brady and Norman have even examined specimens of 3'60 mm. length. 

 This is a size not nearly reached by any of the other known species, and 

 Ibis form therefore still deserves the specific name maxima proposed by 

 Messrs. Brady and Norman. 



