ARIST^US OCCIDENTALIS. 195 



ing posteriorly. External branch Ox*" swirameret much longer than the inner 

 branch, which in turn far surpasses the telson. 



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

 mm. ; antennal scale, 25 mm. ; telson, 18.5 mm. 



Station 3403. 384 fathoms. 1 male. 

 3410. 331 " 2 fern. 



This species appears to be very closely related to Arisfceus antcnnatus * 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 

 carinated 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. occidentalis, as in A. an/ennatus, 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 being as follows : — 



The rudiments of the pleurobranchite of the eighth to the thirteenth 

 somites can hardly be detected except with a lens. They cons^ist of a mere 

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

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

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

 been overlooked by Duvernoy. Setting aside the six almost microscopic 

 rudimentary pleurobranchice and the minute arthrobranchia of the seventh 

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

 as shown on Plate V., Fig. 2, of Duvernoy's memoir.t 



* Penem antennatus Risso, Hist. Nat. des Crustaces des Environs de Nice, p. 96, Plate II. Fig. 6, 1816 ; 

 Aristeus antennatus Duvernoy, Ann. Sci. Nat., 2' Ser., XV. 104, Plate IV. A, V., 1841. 



t As Duvernoy wrote tliirty-eiglit years before Huxley gave us a philosopliical metiiod of describing the 

 complex branchial arrangements among the Crustacea, his statements concerning the point of attachment of 



