96 BULLETIN OF THE 



SKRGESTID.ZE. 



Sergestes arcticus Keoteb. 



Oversigt Vidensk. Sclsk. Forliandl. Kjbbenhaven, 1855, p. (G) ; Monograph. Sergestes, 

 Vidensk. Selsk. Skr., V., Naturvidensk. raatheru. Afh., IV. pp. 240, 276, 

 PL III. figs. 7a -7(7, PL V. fig. 16, 1856. 



Smith, Proc. National Mus., Washington, III. p. 415, 1881. 



Plate XVI. Fig. 4. 



Station. 



N. Lat. 



W. Long. 



Fathoms. 



Specimens. 



304 



41° 35' 0" 



65° 57' 30" 



139 



Fragments only. 



309 



40° 11' 40" 



68° 22' 0" 



304 



1? 



326 



33° 42' 15" 



76° 0'50" 



464 



1 6,19 



337 



38° 20' 8" 



73° 23' 20" 



740 



1 9 , 55 mm. in length. 



In this species there is an epipod and a well-developed podobranchia at the 

 base of the second maxilliped, and above its base a simple lamella in place of a 

 pleurobranchia, a large anterior pleurobranchia with a simple lamella back of it 

 on each of the three succeeding somites, a large anterior and a small posterior 

 pleurobranchia on the antepenultimate somite, and on the penultimate somite 

 two small branchiae, of which the posterior is very much the smaller, while the 

 last somite is without branchiae ; or, indicating the simple pleurolamellse by 

 accents, the branchial formula * may be indicated as follows : — 



Somites. 

 Epipods, 

 Podobranchise, 



VII. 



1 







VIII. 



1 

 1 



IX. 











X. 

 

 



XI. 





 



XII. 

 

 



XIII. 

 

 



XIV. 





 



Total. 



(2) 

 1 



Arthrobranchiee, 









































Pleurobranchige, 







0' 



1' 



1' 



1' 



o 



2 







7 





8+(2) 



* Boas (Studie.r over Decapodernes Stsegtskabsforhold, Vidensk. Selsk. Skr., VI., 

 Natu vidensk. mathem. Afh., I., 1880), for 8. Frisii Kioyer, gives an epipod and a ru- 

 dimentary arthrobranchia for the eighth somite and a single pleurobranchia for each 

 of the succeeding somites including the last. Bate (Ann. Mag. Nat. Hist., 5th ser., 

 VIII. p. 193, 1881), gives, for the genus Sergestes, a " mastibranchia" (epipod) and one 

 pleurobranchia for the eighth somite, a single pleurobranchia for the ninth, a pleuro- 

 branchia and pleurolamella each for the tenth, eleventh, and twelfth, two pleuro- 

 branchise for the thirteenth, and nothing for the last ; but under S. Kroyeri he says, 

 " This species has two well-developed pleurobranchia? attached to the penultimate 

 somite of the pereion, two to the antepenultimate, one plume and a leafiike plate to 

 the next three somites, and one plume and a rudimentary mastibranchial plate to the 

 first pair of gnathopoda " (second maxillipeds). This last statement of Bate would 

 apparently indicate an arrangement of the branchiee much like that which I have 

 given above, or even nearer to that of S. robustus described beyond, but it is very 

 unlike the arrangement indicated by his formula for the genus. 



