7S 



an essential part of the food of several pelagic fishes, for instance the herring 

 and the mackerel. 



Distribution. Coast of France (Canu), British Isles (Brady), Heligoland 

 (Glaus), Kattegat (Lilljeborg), the Baltic (Nordqvist), Atlantic Ocean from Lat. 

 41 to 66 N (Cleve). 



Gen. 21. Isias, Boeck, 1864. 



e Characters. Body moderately slender, with the anterior division 

 somewhat tumid and much vaulted above. Cephalosome well defined from the 

 1st pedigerous segment, but without any distinct cervical depression, front carrying 

 below 2 very delicate, recurved tentacular filaments. Last segment of metasome 

 confluent with the preceding one, and not expanded laterally. Urosome com- 

 paratively slender, especially in male, where it consists of 5 distinct segments, 

 the middle one conspicuously asymmetrical. Caudal rami elongated. Eye -rather 

 large, though not protuberant below. Anterior antenna) not much elongated, 

 otherwise of a structure similar to that in Centropag'es. Posterior antenna) likewise 

 rather similar. Anterior lip with the median lobe remarkably prominent. An- 

 terior maxillipeds less powerfully developed than in Centropages, and having the 

 distal setae not prolonged. Oral parts otherwise resembling in structure those 

 in the above genus. Legs comparatively robust, the 3 middle pairs with the 2nd 

 basal joint of a somewhat unusual appearance, being obliquely oval in form; 

 terminal joint of outer ramus in these pairs with 3 spines outside. Last pair of 

 legs in female with the inner ramus very small, uniarticulate; unguiform projection 

 of outer ramus well marked, though rather short; those in male with the inner 

 ramus obsolete on right side, outer ramus of both legs biarticulate, with the distal 

 joint spatulate in form and considerably larger on the right leg. No ovisac 

 present in female. 



Remarks. This genus, established by Boeck, was placed by Dr. Giesbrecht 

 in his subfamily Temorina 1 , the subfamily Centropagince only comprising the genus 

 Centropages. This arrangement cannot, I think, be admitted, since the present 

 genus in reality exhibits a much closer relation to Centropages than to any of 

 the genera comprised within the subfamily TcmorincK, the structure of the last 

 pair of legs especially seeming to bring it nearer to that genus. AVe do not know 

 at present more than a single species belonging to the present genus. 



