The Lateral Line System in Siluroids. 543 



The mandibular canal of Clarias and Auchenaspis is not piesent 

 in Chaetostomus. 



My observations on the opercular canal of Clarias are unfortunately 

 not complete but comparison of Auchenaspis and Chaetostomus reveals 

 interesting facts. They do not agree quite so closely as in tlie other 

 regions. Firstly a peculiarity is seen in Chaetostomus that no sense 

 organ is present between pores 2 and 3. Secondly if pore 1 corre- 

 sponds to pore 6 of Auchenaspis both being the last in the upper jaw, 

 then probably pores 6 and 8 of the latter correspond to pores 1 

 and 2 of the former. Then however branch 8 of the latter which 

 branches dichotomously would correspond to pore 3 of the 

 former whereas the branch leading to the pore marked l' in Chaeto- 

 stomus and branch 8 in Auchenaspis both run downward and back- 

 ward outside the interoperculura. In the interoperculum 

 in Chaetostomus a sense organ occurs not however represented in 

 Auchenaspis. 



In the innervation the homology of all three forms is complete 

 and a special feature in common is seen in the distribution of the 

 nerve in Chaetostomus and Auchenaspis which proceeds from the great 

 recurrent trunk of the Facial towards the pectoral tin. 



Siluroids and Ami a. The lateral line system has been beauti- 

 fully described by Allis for Ainia and thus a fairly exact comparison 

 is rendered possible. 



Sense organs are far more numerous in Amia than in any of the 

 Siluroids and also the dendritic branching and manifold multiplication 

 of pores is entirely absent in the latter, which therefore in this respect 

 stand at a much lower stage. Again I failed to observe any lines of 

 pit organs but they are in some cases represented by rudimentary 

 branches. Special instances will be detailed below. 



I have tried to make out as far as possible the homologues of 

 the separate organs, estimating the general position, method of 

 branching of the nerves, position in homologous bones, course of the 

 nerve twigs to the organs they supply and lastly the direction in 

 which the branches pass otf from the canals to the pores. The accom- 

 panying table represents the homologies as thus discovered. 



In the infraorbital system the antorbital cross commissure which 

 lies in the dermethmoid in Amia is not present in Siluroids. 



Sense organs 1 and 2 of Clarias and Auchenaspis appear to corre- 

 spond to sense organs 5 and 6 of Amia lying in the antorbital bone, 

 3 of Clarias and Auchenaspis to 8 of Amia in the lachrymal, 4 to 



36* 



