ON THE luciopimelodin;e, a new subfamily of 



THE SOUTH AMERICAN SILURID^.^ 



(Plates II and III.) 



By CHAS. S. driver. 



(Communicated by Prof. Carl H. Eigenmann. Read October 3, 1919.) 



In the Nematognathi or catfishes and their relatives the anterior 

 vertebrae are coalesced and form with the auditory ossicles the so- 

 called Weberian apparatus. This structure has been studied by 

 various authors notably Sagemehl," R. Ramsay Wright^ and Bridges 

 and Haddon.* A brief summary is also given by Boulenger in his 

 " Fishes of the Congo " and in other papers on systematic ichthy- 

 ology by Regan, Eigenmann, et al. Usually the centra of the first 

 three vertebrae are coalesced into one piece without evident sutures. 

 The centra of the fourth, fifth and sixth vertebrae are frequently 

 coalesced with the anterior three, but the sutures between the third 

 and fourth as well as between the fourth and fifth are frequently 

 quite evident, especially in the 3^oung. 



The coalesced first to third vertebrae are without lateral processes 

 The fourth and fifth have various processes. 



As in all other members of the Nematognathi, the centra of the 

 anterior vertebrae of the species of the Pimelodinae, a subfamily of 

 South American catfishes, are coalesced. The lateral processes of 

 the fourth, fifth and sometimes the sixth vertebrae are expanded, 

 sometimes largely separated from each other, more frequently joined 

 to each other to form an osseous shield or roof over the anterior part 

 of the abdominal cavity. 



In Rhamdia of the Pimelodince there are three processes distinct 



1 Contribution from the Zoological Laboratory of Indiana University, 

 No. 166. 



- Morpholog. Jahrb., Bd. X. 



3 Trans. Roy. Soc. Canada, 1885. 



* Phil. Trans. Roy. Soc, B, 1893. 



448 



