68 ME. W. S. EOWNTEEE ON THE 



The following is a summary of my observations on the other Physostomi : — 



1. Salmo. Salmo trutta (3 specimens) and Salmo fario (1 specimen). — Duct short; 

 opens distinctly on the right side of the dorsal wall of the oesophagus (PI. 4. fig. 19). 



2. COREGONUS. Coregonus albus (4 specimens). — Duct of moderate length; opens 

 nearly medially, doubtfully to the right side. 



3. OsMERUS. Osmerus eperlanus (3 specimens). — Duct rather long ; opening apparently 

 median. 



4. Thymaelus. Thymallws vulgaris (2 specimens). — Duct rather short ; opens slightly 

 to the right side. 



5. MormtriDtE. Petrocephalus bane (2 specimens) and Gymnarchus nilotictis (4 

 specimens). — In both these forms the short, wide duct opens into the oesophagus laevo- 

 dorsally. In Petroceplmlus (fig. 20), the connection of the duct with the air-bladder is 

 also on the left side. In Gymnarchus (fig. 21), which, by the way, has been erroneously 

 included in the Ostariophyses by Bridge and Haddon in the paper previously referred to, 

 as also by Wiedersheim *, this is not the case, and the connection with the oesophagus is 

 more nearly median than in Fetrocephalus. 



6. NoTOPTERUS. Notopterus kapirat (2 specimens). — The duct opens into the 

 oesophagus far forward, and slightly Init distinctly to the left side (fig. 22). It is 

 short and wide, and opens also into the left side of the air-bladder itself, which 

 is longitiidinally divided in the abdominal region by a vertically complete median 

 septum. This septum has a free edge anteriorly, not quite reaching the transverse 

 membrane, which partially separates this part of the bladder from the unpaired 

 anterior chamber, and it is just on a level with this free edge that the ductus pneumaticus 

 opens. These relations, with others not now before us, agree with those described by 

 Bridge f as existing in Kotopterus borneensls, with the excejition that in that form the 

 pneumatic duct is described as being connected with the oesophagus in the mid-dorsal 

 line. 



7. Elops. Elops saurus (2 specimens). — The air-bladder opens by a wide orifice, 

 rather than by a definite duct, into the stomach at about the middle of its length, just 

 behind the pyloric flexure, and in the front part of the very long blind sac. In one 

 specimen the opening was in the mid-dorsal line ; in the other, the stomach was 

 irregularly shaped, and it became a mere matter of opinion whether the connection 

 ought to be regarded as median or laevo-dorsal. Setting aside this doubtful case, we must 

 take the evidence of the other as pointing to a median position of the duct (fig. 23). 



8. Albula. Albula conorhynchus (1 specimen). — In this fish, primitive in the 

 possession of a valved conus, the duct is longer than in Elops, and opens into the 

 stomach much farther back, quite near, but not at, the extremity of the blind sac. 

 It is in the mid-dorsal line (fig. 24). 



* ' Elements of Comp. Anat.,' translation by W. N. Parker, 2ud edition, 1897, p. 226. 



t " The Air-bladder and its connection with the Auditory Apparatus in Notopterus borneensis," Journal of the 

 Linnean Society, Zool. vol. xxvii. 1900, p. 507. 



