I. '08. 32 



with spines, with which the long median style is furnished on 

 its inner aspect. The male also possesses the usual small lobe 

 at the base of the second pair of pleopods. 



The outer uropod (fig. 16) is rather less than one-third 

 longer than the inner, and, in adults, is usually more than five 

 times as long as broad. ^ The external margin is distally ciliate 

 for less than one-third the length of the uropod ; a short spine 

 emphasises the division between the naked and setose por- 

 tions. 



Size. — Tlie largest specimen found off the Irish coast is 

 47 mm. in length; I have, however, examined a female which 

 measured 65 mm. 



Colour in life. — The walls of the carapace are transparent, 

 with a few small scarlet red chromatophores ; the black stomach 

 and scarlet hepatic and cardiac regions show through very dis- 

 tinctly. There are a few red chromatophores on the first two 

 abdominal somites, and there is a faint suffusion of the same 

 colour on the remaining somites, telson, and uropods. The 

 cornea is jet black. The joints of the antennular peduncle are 

 transparent, but are tinged with red on their outer distal mar- 

 gins ; the antennal scale is perfectly transparent, and all three 

 pairs of flagella are reddish. The mandibles, maxillae, and 

 first two pairs of maxillipedes are red ; the third pair and the 

 first three pairs of pereiopods are dotted with red ; the last two 

 pairs of pereiopods are very faintly suffused wdth the same 

 colour. 



A fuller synonymy than is found above is given by Steb- 

 bing (1905), but Lo Bianco's record of Sergia magnifica, which 

 is included, has been referred by Senna (1903) to Sergestes 

 vigilax, Stimpson. An additional synonym is S. Binhi, 

 Kroyer, which Hansen states is the masfigopus of S. arcticus. 



General distribution. — In the Atlantic Ocean Sergestes 

 arcticus is common and widely distributed ; it is known from 

 Lat. 65^ 20' N. (Hansen), and as far south as 40 miles off 

 Table Mt. (Stebbing), and Lat. 38° 5' S. (Hansen). The 

 species has been recorded from the Mediterranean, and three 

 specimens were found by the Challenger to the south of Aus- 

 tralia (Hansen). 



I have examined specimens taken by the Thor at the follow- 

 ing localities : — 



2 1 /5/'05.— 47° 47' N., 8° 0' W., soundings 454-881 fathoms. Mid- 

 water trawl, 0-274 fathoms — Twenty-one, 22-28 mm. 



28/5/'05.— 61° ir N., 11° 0' W., soundings 527 fathoms. Mid- 

 water trawl, 0-492 fathoms — Three, 30-49 mm. 



28/8/'05.— 63° 42' N., 13° 2' W., soundings 360 fathoms. Mid- 

 water trawl, 0-35 fathoms — Five, 14-22 mm. 



' In a very large female the outer uropod is a trifle less than five 

 times as long as broad. 



