SILURIDiE. THE PIMELODIN^. 343 



row : the back, between the first dorsal and the caudal, 

 has a tuberculated bony ridge : the vent is before the 

 middle. The dorsal fins are two : the anterior has the 

 first dorsal ray hard at the base, but soft at its point, 

 the hinder part being indented ; the second dorsal has 

 only one short prickle, with a short membrane behind : 

 the pectoral spine is strong and doubly serrated ; ventral 

 fins small ; anal fin of six rays only. The caudal fin is 

 very remarkable: it is lunate, and of ten rays; the 

 uppermost one of which is so much prolonged, like a 

 whip or rod, as to exceed the whole length of the head 

 and body. This great developement of the caudal or tail 

 fin, and the partially mailed plates upon the nape, lead 

 to the belief that this extraordinary fish forms the pas- 

 sage, in conjunction with Synodontes, between the Lori- 

 cariYKB and the Pimelodince. We have not, however, 

 yet seen a specimen ; and unfortunately Dr. Hamilton's 

 description, which we have here abridged, is unaccom- 

 panied by any figure. There is some distant resem- 

 blance between Sisor and the Silurus Bagre of Bloch : 

 this latter, however, we shall for the present keep dis- 

 tinct, under the name of Breviceps. In this the cau- 

 dal fin is also lunate ; but the points are not extended, 

 like those of the first dorsal and pectoral rays, which 

 reach to a very considerable length : the head is par- 

 ticularly short and obtuse, with the eyes very remote; 

 and there are only two pairs of cirri, one of which is 

 very short. The upper jaw is slightly longer than the 

 under : it is very large, and armed with numerous sharp 

 teeth, very small, placed in two broad rows on the upper 

 jaw, and in one on the under : finally, the tongue is 

 very large, thick, and rounded. We mention these par- 

 ticulars in this place, from a belief that this type shows 

 us the fissirostral genus of the Pimelodince, or that by 

 which the sharks are represented in this sub-family. 

 The third genus is that by which we distinguish the 

 Pimelodus cyclopium of Humboldt {Cyclopium Hum- 

 holdtii ^w.jjig. 83.), which, because it has an adipose fin, 

 has been siafiered until now to remain unnoticed, even as 



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