89 



Inferior antenna; attaining the length of the body, not including the terminal seg- 

 ment of metasome, flagellum scarcely more than x / 3 as long as the last peduncular 

 joint, and having the 1st articulation twice as long as the other 2 combined. 

 Male much smaller than female, and extremely slender, with the middle segment 

 of mesosome narrow cylindric in form, and quite smooth. Superior antennae with 

 the flagellum much larger than in female, and provided with a greater number of 

 olfactory filaments. Colour yellowish, clouded with irregular dark brown shadows. 

 Length of adult female reaching 20 mm., that of male scarcely more than half 

 that size. 



Remarks. — The present species was first described by Sowerby in the above 

 quoted paper under the name of Oniscus longicornis. It is, however, very probable 

 that the form observed by the Rev. Charles Cordiner several years previously, 

 and named AstaciUa. without any specific denomination, was the very same species. 

 The form recorded by Johnston as Leacia laeertosa, is undoubtedly this species. 

 By most of the earlier authors, it has been referred to the genus Arcturus of 

 Latreille. The Arcturus gracilis of Groodsir is, in my opinion, nothing else than 

 the adult male of the present species. From the other Norwegian species, it may 

 be chiefly distinguished by its slender and elongated body, and by the rather 

 slight development of the dorsal tubercles. 



Occurrence. — This species would seem to occur along the whole coast of 

 Norway, from the Christiania Fjord to Vadso. It is generally found in moderate 

 depths, ranging from 10 to 30 fathoms, clinging to Hydroida and Polyzoa, several 

 specimens, females, males and young, being often associated in the same colony. 

 By the aid of its 3 posterior pairs of legs, the animal is capable of getting a 

 rather firm hold on the object to which it is clinging, moving the fore part of its 

 body freely to and fro in search of food, which is first seized by the long pediform 

 inferior antennse. At times it is seen to leave go its hold, and to start off rather 

 rapidly through the water, in order to affix itself on some other place. This motion 

 is effected by the aid of the 2 anterior pairs of pleopoda, which in such cases 

 are protruded from the shelter of the valvular uropoda, and push the animal 

 forwards. Not infrequently female specimens are found carrying their young brood 

 affixed all round the long inferior antennae, which thereby acquire a peculiar 

 velvety appearance. 



Distribution. — British Isles (Sp. Bate), Kattegat (Meinert), Iceland. 



12 — Crustacea. 



