FISHES OF THE FAMILY LOEICAEIIHE. 307 



\ Subfamily V. Aegii n m. 



Vertebrae below tbe dorsal fin with bifid neural spines ; those above the anal with 

 bifid haemal spines ; lower and fourth upper pharyngeals toothed ; teeth in the jaws 

 in more than one series ; no pseudobranchiae ; body naked; anterior rudimentary ray 

 of ventral represented by a small internal rounded plate. 



The Argiina? are to be regarded as degraded or ultra-specialised forms closely 

 related to the Neoplecostominae, from which they differ mainly in the naked body and 

 the stronger ribs. The structure of the adipose fin, which is in some species composed 

 of a well-developed movable spine, attached posteriorly by a membrane to the caudal 

 peduncle, is sufficient eudence that the nakedness of the body is a secondary and not a 

 primitive feature. The neural and haemal spines are somewhat less expanded than in 

 the other subfamilies, whilst there is also a slight difference in the structure of the 

 suspensory apparatus, the pterygoid being small, instead of large and connected with 

 the prefrontal, as in the armoured forms. The clavicles and coracoids run somewhat 

 forwards to their symphysis, whilst in the other subfamilies their lower portions lie 

 transversely between the bases of the pectorals. 



Key to the Genera. 



Ventral fins present 16. Arges C. & V. 



Ventral fins absent 17. Astroblepus Humb. 



16. Arges. 



Cychpium 1 Swainson, Nat. Hist. Fishes, ii. 305 (1839) ; Eigenm. & Eigenm. Proc. Cal. Ac. (2) 



i. 1888, p. 164, and Occ. Pap. Cal. Ac. i. 1890, p. 350. 

 Arges Cuv. & Val. Hist. Nat. Poiss. xv. p. 340 (1810) ; Griinth. Cat. Fish. v. p. 222 (1861). 

 Brontes Cuv. & Val. t. c. p. 341 ; Giinth. t. c. p. 224. 

 Slygogenes Giinth. t. c. p. 223. 



Body oblong or elongate ; eye's small, superior. Dorsal originating above or a little 

 in front of or behind the ventrals, with I 6 rays ; anal with I 5-6 ; pectoral with 

 I 9-12; ventral with I 3-4. Caudal truncate or slightly emarginate, with the outer 

 rays a little produced. Adipose fin 2 , if present, either represented by a movable 

 spine, posteriorly attached by a membrane to the caudal peduncle, or by a long more 

 or less developed fin, with or without a small or rudimentary imbedded spine. 

 Vertebrae 5 + 12 + 17 (in A. festce). Ribs fairly strong. 



Andes of Peru, Ecuador, Colombia, and Venezuela. 



1 Swainson established the genus in these words : — " The third genus is that by -which we distinguish the 

 Pimelodus eyelopium of Humboldt (Cyclopium humboldtii Sw.)." His generic name, being derived from 

 the genitive plural of Cyclops, is as inadmissible as would be that of Silurorum. 



2 Those who regard the adipose fin as a primitive feature, perhaps inherited from a common ancestor by the 

 Siluridse and other Fishes possessing it, should note how in the geuus Arges a modified and reduced adipose 

 fin like that of the armoured Loricariidas becomes replaced by a long and well-developed fin exactly similar to 

 that of a 1'imeludus. 



