^ 



196 



STALK-EYED CRUSTACEA. 



Two of the ^^ Challenger" Peneids assigned to the genus Aristceus by Bate, 

 viz. A, armattis and yl. rostridcntatuSy and the two species * doubtfully referred 

 to the same genus by Smith differ from the true species of Aridams in some 

 important respects : the penultimate pair of thoracic appendages are fur- 

 nished with epipods; the antepenultimate pair bear a podobranchia; and there 

 are functional pleurobranchia) on each somite from the eighth to the four- 

 teenth, the branchial formula in these species being as follows: — 



Somites 



Pleurobranchiae 



Artlirobrancliia3 



Podobranchiae 



Epipocis 



VII. VIII. 





 1 

 

 1 



1 

 1 

 1 

 1 



IX, 



1 

 2 

 1 

 1 



1 



2 

 1 

 1 



XI. 



1 

 2 

 1 

 1 



XII. XIIJ. XIV. 



1 



2 

 1 

 1 



1 



2 

 

 1 



1 

 

 

 



7 



12 



5 



(7) 



24 + (7) 



The peculiarities here exhibited appear to be of generic import, and 



these species should be placed together in a genus distinct from Anskms, to 



which Bate's provisional name Plesiopcneus ^ may be applied. Pcneus edward- 

 danus Johnson^ assigned to the genus Aristceus by MierS;§ has the terminal 



segment of the mandibular palpus bilobed as in the s^idQXQS oi Plesiopeneus, 

 and very probably belongs to the latter genus. 



Two of the species [A. semidentatus and A. tomentosus) included in the 

 genus Aristwus \_Plcsiopeneus] by Bate in 1881, were transferred to Ilcmipeneus 

 in the final " Challenger" Report of 1888. I suspect that these two species, 

 together with Ilemiperieus virilis Bate, which is probably the male of H. tomen- 



the gills must not be taken too strictly. He assigns anterior arthrobranchia; to tLe appendages and posterior 

 arthrobrancbife to the body wall. His description and figure of the gills of A. antennatm are misinterpreted 

 by Professor Smith (Ann. Eep. U. S. Fish, Comm. for 1882, p. 409), whose hypothetical formula involves 

 twenty-one gills, while Duvernoy states the number to be sixteen. My interpretation of Duvernoy's figure, 

 by aid of the light thrown upon it by A, occidentalism is as follows (the Roman numerals are the index num- 

 bers of the gills in Duveruoy's figure) ; 



I. 



II. 

 III. 

 IV. 



V. 



VI. 



VIL 



VIIL 



Podobranchia of 8th somite. 

 Anterior arthrobranchia of 9th somite. 

 Podobranchia of 9th somite. 

 Anterior arthrobranchia of 10th somite. 

 Podobranchia of 10th somite. 



Anterior arthrobranchia of llth somite. 



Podobranchia of Uth somite. 



Anterior arthrobranchia of 12th somite. 



IX. Posterior artbrobrancliia of 12th somite, 



X. Anterior " " I3th " 



XL Posterior " " 13th « 



XTT. Pleurobranchia of 14th somite. 



XIII. Arthrobranchia of 8th somite. 



XIV. Posterior arthrobranchia of 9th somite. 

 XV. ** « of 10th " 



XVI. « '* of 1 1 th " 



* Aristmm? tridens Smith, Ann. Rep. U. S. Pish Comm. for 1882, p. 104, Plate TX. Pig. 1-6, 1884; 

 and Aristceus ^ foUaceMS Smith (= Tenetis foliaceus Risso?), Proc U. S. Nat. Mus., VIIL 188, 1885. The 

 former species is identical with A. armatus Bate. 



t Ann. Mag. Nat. Hist., 5th Ser., YIII. 188, 1881. The type of Flesiopcueus is Amtam armatus Bate. 



X Proc. Zoolog. Soc. London, 1807, p. 897. 



§ Proc. Zoolog. Soc. London, 1878, p. 308, Plate XVII. Pig. 3. 



L , 



