go CRUSTACEA MALACOSTRACA. III. 



a. First or second segment not half as broad again as sixth segment. 



. Abdomen with the margin just outside the base of each nropod convex or straight. 



f. Antennal squama long at least about as long as the diameter of third peduncular 

 joint Head at least six times as broad as the distance between the anterior ends of 



the keels limiting the front area 2. N. oblongus G. O. Sars. 



ff. Antennal squama conspicuously shorter than the diameter of third peduncular joint. 

 Head about four and a half times as broad as the distance between the anterior ends 



of the keels limiting the front area 3. N. arcticus n. sp. 



. Abdomen with the lateral margin just outside the base of each uropod considerably con- 

 cave, as the posterior median part of the abdomen is produced backwards. 4. N. analis 



n. sp. 



/?. First and second segments conspicuously more than half as broad again as sixth segment. 



5. N. laticeps n. sp. 

 b. Surface of the body with a reticulate network 6. N. reticulatus n. sp. 



Section II. 



A. Second joint of the antennulse terminates in short or moderately long processes leaving nearly 

 the entire fourth joint uncovered. Abdominal operculum posteriorly rounded or straight 



a. Posterior ventral area of the thorax without any process. 



a. Antennular vesicle very long and narrow, between two and a half and three times as long 

 as broad. Uropods with the endopod much longer than the exopod ... 7. N. inermis n. sp. 



y9. Antennular vesicle pyriform, not half as long again as broad. Uropods with the endopod 

 slightly longer than the exopod 8. N. ceqiiiremis n. sp. 



b. Posterior ventral area of the thorax with a large, curved, acute process, but without any se- 

 cond process. 



a. Postero-lateral margin of the abdomen without any incision or tooth. 



. First pair of legs moderately slender, without strong spines on the lower margin of fifth 



joint 9. N. plebejus n. sp. 



. First pair of legs extremely thick, with two very long and robust spines on the lower 



margin of fifth joint 10. N. crassipes n. sp. 1 



/9. Postero-lateral margin of the abdomen at each side with an incision and a very conspicuous 

 triangular angle or tooth n. N, minutus n. sp. 



c. Posterior ventral area of the thorax with an extremely large, curved, acute process, and in front 

 of this in the median line a long, slender and straight process 12. N. armatus n. sp. 



B. Second joint of the antennulae terminating in long, oblong-triangular processes overlapping the 

 fourth joint. Operculum posteriorly angular or even produced in an acute process. 



a. Anterior margin of the front area nearly half as long as the breadth of the head. Fourth joint 

 of the six posterior pairs of legs terminating in a short seta 13. N. spinicornis n. sp. 



1 This species, which has been briefly mentioned on p. 87 88, is established on the so-called male of N. otlongus 

 figured by Sars on PI. 50. His figures and description are quite sufficient for recognizing this fine species, which has not 

 been taken out of Norway. 



