1. '08. 24 



Thor. 



30/5/'06.— 51° 27' N., ir 10' W., 110 fathoms. Trawl— One, 

 51 mm. 



Vertical range. — S. siphonocera is found commonly in the 

 Mediterranean between 30 and 100 fathoms, and has been 

 taken in deeper water up to 400 fathoms (Adensamer). 

 Smith's Venezuelan specimens w^ere caught in 31 fathoms, 

 while in the Bay of Biscay the species w^as found in 218 

 fathoms. 



Family SERGESTIDAE, 



Genus Sergestes, H. Milne-Edwards. 



Sergia, Ortmann. 



Fifteen years ago our knowledge of this genus was in a 

 state of great confusion, for the literature abounded in de- 

 scriptions of species founded only on immature specimens. 

 It is entirely due to Hansen's important revision (contained 

 in two papers, 1896 and 1903 (1)) that this unsatisfactory con- 

 dition of things no longer exists. Hansen was able to connect 

 a large number of described larvae with their adults, thus 

 making a very considerable reduction in the total number of 

 known species, and he also drew attention to the importance 

 of certain characters, of great specific value, w^hich had pre- 

 viously been neglected. 



Two species of Sergestes, S. rohustus and S. arcticus, have 

 been found off the Irish coast ; both belong to that section of 

 the genus which is characterised by Hansen thus : — 



TJiird maxillipede at most hut little longer, sometimes 

 shorter, than third pereiopod, its first joint rarely, the 

 second-fourth joints never obviously incrassated in pro- 

 portion to the joints in the third pereiopod; its two distal 

 joints with numerous bristles along both margins. On 

 the outer uropod the ciliated part never occupies half the 

 exterior margin. The body not very long and slender; 

 the distance between eyestalks and mandibles not very 

 long. The first joint of the antennular peduncle con- 

 siderably or much longer than third. 



The two species may be readily distinguished from one. 

 another by the following characters : — 



I. Eostrum reaching almost to middle of 

 corneal portion of eye ; no post-ocular 

 spine, gastro-hepatic groove very faint ; 

 second and third joints of antemiular 

 peduncle stout; antenna! scale but little 

 narrow^ed apically and less than three 

 times as long as broad ; fifth pereiopod 

 almost two-thirds the length of the cara- 

 pace (excluding rostrum) ; outer uropod 

 four to four and a half times as long as 

 ^^o^^' • • • • . S. robustus (p. 25). 



