f 





AEISTiEUS OCCIDENTALIS. 



195 



ing posteriorly. External branch of swimmeret much longer than the inner 

 branch; which in turn far surpasses the tclson. 



Length, 158 nun. ; carapace, including rostruiU; 85 mm. ; rostrum, 49 



mm. ; antcnnal scale, 25 mm. j telson, 18.6 mm. 



Station 3403. 384 fathoms. 1 male. 



ii 



3410. 331 



Hi 



2 fern. 



This species appears to be very closely related to Arisfccus anfennatus 



* 



of 



the Mediterranean Sea. Risso's description and figure of the latter species 

 are too faulty to be of any service for comparison. By comparison with 

 Duvernoy's figures it appears that the Pacific species differs from the Medi- 

 terranean in having a much longer and more upwardly inclined rostrum, a 

 carlnatcd and posteriorly toothed sixth abdominal segment, and much longer 

 abdominal appendages. These differences, taken in connection with the 

 remote habitats, leave little doubt that the two forms are specifically 



distinct. 



In any event, there is no doubt that they are strictly congeneric. In 

 A, oceidenlalls, as in A. anieunatus, according to the detailed account of Duver- 

 noy, there is no epipod on either the ultimate or the penultimate pair of legs, 

 the branchial arrangement in A, occidentalis beiniir as follows : 



Somites 



Pleiirobranchia) 



Artlirobranchia3 



rodobrancliioo 



Epipods 



VII. VTIT. IX. 



■^ 





 1 

 



1 



r 

 1 

 1 

 1 



r 



2 

 1 

 1 



X. 



r 

 2 

 1 

 1 



C3 



XI. XII. XIII. XIV, 



r 

 2 

 1 

 1 



r 



2 

 

 1 



r 



2 

 

 



1 

 

 







1 + Gr 



12 

 4 



(6) 



^ 



■^ 



IT + Gr-j-iG) 



The rudiments of the pi 



■\ 



obranchia^ of the eighth to the thirteenth 



somites can hardly be detected except with a lens. They consist of a mere 

 vestige of the stem of the gill, without any lateral filaments excepting m 

 those of the eighth nnd ninth somites. The single arthrobranchia of the 

 seventh segment, although functional, is very small and might easily nave 

 been overlooked by Duvcrnoy. Setting aside the six almost microscopic 

 rudimentary pleurobranchiae and the minute arthrobranchia of the seventh 

 somite, the gills agree in number and position with those of A. antennatns 

 as shown on Plate V., Fig. 2, of Duvernoy's mcmoir.f 



* Pcneus anlennatus EIsso, Hist. Nat. dcs Crustac^s des Environs dc Nice, p. 90, Plate II. Fig. 6, 1816 ; 

 Aristeus anUmatus Duveruoy, Aim. Sei. Nat., 2" Ser., XV. lOl, Plate IV. A, V., 1841. 



t As Duvcrnoj wrote tliirty-cigl.t years before Huxley gave us a philosophical nieihod of dcscribuig tiie 

 complex branchial arrangenicuts among the Crustacea, his statemeuts concerning ihe point of attachment ot 



