544 "• K- I'OI^LAHD, 



1(» in the suborbital, 5 to 11 in the (lower) postorbital. The branch 

 in Clarias which proceeds out between sense organs 4 and 5 corresponds 

 to pore 11 in Amia. This branch must be regarded as the 

 last rudiment of a canal represented in Amia by the 

 vertical line of pit organs. 



The homology of the first sense organ in Chaetostomus is not clear. 

 The rest correspond as in Clarias and Auchenaspis. 



The branch, so long in Clarias, which terminates at pore 6 

 corresponds to pore 12 in Amia and appears also to be the 

 rudiment of a canal represented in Amia by the hori- 

 zontal line of pit organs. 



Sense organ 14 of Amia is not present in the three forms Clarias, 

 Auchenaspis and Chaetostomus but occurs in Trichomycterus and 

 Callichthys as also does the pore represented in Amia by the system 

 of pores 15 — 7. 



The first two organs of the supraorbital system lie in the nasal 

 bone median to the nose. In Amia 3 organs are present in the same 

 bone. It appeared to be a fairly constant phenomenon that the nerve 

 twig supplying the first organ in Siluroids approaches it from the 

 median side. It is not recorded if this is the case in Amia. There 

 can be little doubt that organ 4 of the Siluroids corresponds to 5 of 

 Amia for pore system 6 in the latter runs medianly in the centre of 

 the frontal bone as does the branch in Auchenaspis. Even in Amia 

 where more sense organs as a rule are present sense organ 5 of Clarias 

 is not represented. 



The branch passing towards the crown of the head and containing 

 one sense organ is exactly homologous in Amia and the three Siluroids 

 chiefly under consideration. 



In the main canal organs 15 and 16 of Amia are represented 

 by a single organ in the Siluroids the Ramus oticus being evidently 

 homologous. Behind this point in all the forms the operculo-man- 

 dibular joins with the main line within the squamosal. No pore is 

 present however at the point in the Siluroids. It is hard to say 

 which is the more primitive — absence of a simple pore or presence 

 of a secondary multified pore system. 



The organ supplied by the Glossopharyngeus is evidently homo- 

 logous throughout as also is that supplied by the 1st branch of the 

 Vagus. In sections I could discover nothing in the Siluroids to represent 

 the middle pit line nor is a supratemporal cross commissure present. 

 On the other hand in Amia there is no representative of the remarkable 



