HYPOSTOMATINA. 221 



Sixth Subfamily. 



SILURIDiE PROTEROPODES. 



The rayed dorsal fin is always present and rather short; the 

 ventrals are inserted below (in all the genera, except Acestra), or 

 in front of, the dorsal (Acestra). The gill-membranes are confluent 

 with the skin of the isthmus, the gill-opening being reduced to a 

 short slit. Pectorals and ventrals horizontal. Vent before, or 

 not much behind, the middle of the length of the body. 



Thirteenth Group. HYPOSTOMATINA. 



Proteropodal Siluroids with the anterior and posterior nostrils 

 close together, and generally with a short flap between them. 

 The lower lip is reverted and much dilated, forming a broad flap 

 more or less deeply notched in the middle. 



The union of apparently such different genera as Arges, Callichihys, 

 Loricaria, &c, is so opposed to the views of former ichthyologists, 

 that it will be necessary to add a few words in explanation. The 

 mailed body of the Loricariae and Hypostomes, reflected in some way 

 internally by the skeleton, is a very striking character : so much so. 

 thai, Kner is inclined to separate them from the Siluroids altogether, 

 and Bleeker forms of them his first Siluroid family. However, that 

 the development of dermal scutes is not a character of so much value, 

 is not only proved by Doras, where similar dermal productions cover 

 a part of the lateral line, and by the numerous modifications of the 

 dermal carapace on and behind the occiput, but especially by the 

 Indian genus Sisor, which has a series of dorsal plates, the sides 

 being almost naked. With regard to the skeleton, the compression 

 of the caudal vertebrae and the dilatation of their neural portion are 

 not only found in Loricaria and Hypostomus, but also in other slender- 

 tailed Siluroids, as Sisor, Bunocephalus, and Aspredo, genera which we 

 associate with the former, but which are excluded from the Lorica- 

 roids of Kner and Bleeker. 



Every doubt that Loricaria and the genera allied to it are true 

 Siluroids, and nothing but Siluroids, must disappear when they are 

 compared with those with which they have been associated by 

 myself. There we find the gill-opening reduced to a foramen or 

 short slit, in consequence of the gill-membranes being confluent 

 with the skin of the broad isthmus ; the nasal openings placed close 

 together in a small groove ; the ventrals inserted far forwards, 

 below, or even in front of, the short dorsal ; the pectorals and ven- 



