ARISTZUS OCCIDENTALIS. 195 
ing posteriorly. External branch of swimmeret 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. 
Se SLO 233L~ 176 2 fem. 
This species appears to be very closely related to Aristeus antennatus * 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. antennatus, 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 : — 
Somites Vile \alls ae 92 206 Say scoir, Sony 
Pleurobranchize 0 r r r r r , 1 = 1+46r 
Arthrobranchiz i! 1 2 2 2 2 2 0 = 12 
Podobranchize 0 i 1 1 a 0 0 Oo= 4 
Epipods 1 1 1 al il al 0 0= (6) 
17 + 6r + (6) 
The rudiments of the pleurobranchiz 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 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 pleurobranchie and the minute arthrobranchia of the seventh 
somite, the gills agree in number and position with those of A. antennatus 
as shown on Plate V., Fig. 2, of Duvernoy’s memoir.+ 
* Poneus antennatus Risso, Hist. Nat. des Crustacés des Environs de Nice, p. 96, Plate II. Fig. 6, 1816; 
Aristeus antennatus Duvernoy, Ann. Sci. Nat., 2° Sér., XV. 104, Plate IV. A, V., 1841. 
+ As Duvernoy wrote thirty-eight years before Huxley gave us a philosophical method of describing the 
complex branchial arrangements among the Crustacea, his statements concerning the point of attachment of 
