I. '08. 28 



is shown in fig. 11, and in the same sex a small lobe with a 

 few setae is also found at the base of the endojiod of the 

 second pair of pleopods. The outer uropod (fig. 10) is almost 

 one and a half times the length of the inner ; in an adult 

 female it is just four times as long as broad. The external 

 margin is distally ciliate over a distance less than one-third 

 the total length of the uropod. 



Size. — The lai-gest specimen observed is a female measur- 

 ing 87 mm. ; Hansen (1908) records a specimen 90 mm. in 

 length. 



Colour in life. — Uniform clear scarlet lake, much darker, 

 with bluish reflections, on the anterior portions of the cara- 

 pace. The antennal scale is scarlet lake with a row of faint 

 crimson spots ; similar spots are also found along the basal 

 edge of the sixth abdominal somite and near the apices of the 

 inner and outer uropods. The eyes are jet black, and all the 

 finer setae with which the species is clothed are reddish gold. 

 Sergestes rohustus probably possesses the finest colouring of 

 any of the deep-water prawns found off the west coast of 

 Ireland. The blue reflections are very conspicuous and beau- 

 tiful ; though most marked on the anterior parts of the cara- 

 pace, they can be detected over the whole of it and on the 

 abdomen also. 



Alcock has suggested (1901) that Sergestes hisulcatus, 

 Wood-Mason, is a synonym of this species, and Miss Rathbun 

 (1906) has included it under her synonymy of S. rohustus. I 

 am unable to agree with this view. The definite cervical 

 groove and the forms of the rostrum, secondary flagellum of 

 the male, antennal scale and petasma in S. hisulcatus (all 

 figured by Faxon, 1895, pi. Lii.) offer ready means of dis- 

 tinguishing it from the form here described. In particular, 

 attention is drawn to the petasma, which, as described by 

 Alcock and figured by Faxon, shows just as great differences 

 from that of S. rohustus as exist between the latter species 

 and Sergestes arcticus. 



General distribution. — Sergestes rohustus has been recorded 

 by Smith from the east coast of the United States between 

 Lat. 34° 28' and 39° 38' N., and Long. 68^ 21' and 75° 22' W. 

 It has been found in the Mediterranean near Crete (Aden- 

 samer) and in the neighbourhood of Sicily (Lo Bianco and 

 Riggio) and was taken in the Bay of Biscay by the Caudan 

 Expedition (Caullerv). Further north it is known from Lat. 

 59^ 49' N., Long. 9° 46' \V., and S.W. of the Faroes in Lat. 

 61° 8' N. (Hansen). Miss Rathbim has recorded speci- 

 mens under this name from the vicinity of the Hawaiian 

 Islands; it is, how^ever, very probable that these examples 

 should be referred to a distinct species, S. hisulcatus. If this 

 is so, S. rohustus, as at present understood, is restricted to the 

 Atlantic Ocean and Mediterranean. 



