222 silurid.i:. 



trals horizontal ; a short anal ; the remarkable development of the 

 lower lip ; and, finally, the anterior vertebrae never coalescent into 

 one large one, the first being somewhat large*" than the others, and 

 provided with large transverse processes. A combination of such 

 characters indicates a natural affinity even when we consider other 

 points as being of minor importance, such as the spiny covering of 

 the first ray of the fins of Arges, Stygogenes, &c, which is identical 

 with the spiny armature of the Hypostomes and of some Loricarise ; 

 the spinous adipose fin of Slygogenes ; the size of the mature eggs, 

 which is equal in Arges and Loricaria ; &c. Thus, I consider Arges 

 as a naked Loricaria, or, vice versa, Loricaria as a mailed Arges ; and 

 although these forms are sufficiently diversified to admit of further 

 subdivision, it is a most artificial method, by which their natural 

 union is destroyed. 



a. Head and body entirely covered with soft skin ; maxillary barbels 

 only : Argina. 



88. ARGES. 

 Arges, Ciiv. 8f Val. xv. p. 333. 



Adipose fin low, elongate ; dorsal short, without pungent spine ; 

 anal short. Teeth, small, slightly curved, notched at the apex, 

 forming a narrow band in each jaw ; palate toothless ; cleft of the 

 mouth of moderate width, with a maxillary barbel on each side ; a 

 short, broad flap on each side between the nostrils ; lower lip very 

 broad, pendent. Eyes small, covered with transparent skin. Head 

 covered with soft skin. Gill-openings not extending downwards to 

 the throat, separated by a broad isthmus. Ventrals six-rayed, in- 

 serted below the dorsal. 



Andes. 



1. Arges sabalo. 

 Cuv. $ Val. xv. p. 335. pi. 444. 



B. 4. D. 1/6. A. 1/6. P. 1/12. V. 6. 

 The length of the head is one-fourth of the total* ; the eyes are 

 situated at the end of the second third of the length of the head ; 

 nostrils in the middle between the eye and the end of the snout. 

 Ventral fins somewhat in advance of the dorsal, below the posterior 

 third of the pectorals. Brownish, marbled with blackish above. 

 {Val) 



Andes of Peru. 



2. Arges brachycephalus. 

 Gunth. Proc. Zool. Soc. 1859, p. 92. 



B. 4. D. 1/C. A. 6. P. 1/9. V. 6. Vert. 13/16. 

 The length of the head is one-fifth of the total ; the eyes are situ- 

 ated nearly in the middle of the length of the head ; the nostrils are 

 much nearer to the extremity of the snout than to the orbit : ven- 



* One-fifth according to the figure. 



