1896.] MB. r. E. BBDDABTl ON dissttha bpisoopus. 231 



This state of affairs I have found in certain Hornbills and in many 

 Owls. At present I have not surveyed the principal groups 

 of birds from this point of view ; but some years since I described 

 the same thing in a Penguin. Apart from this latter instance, 

 which I hope to have the opportunity of re-examining, it is 

 interesting to find a likeness between the Passeres and the Picarian 

 birds, and between both and the Owls. 



As to the homologies of this structure outside the Class 

 Aves, I am inclined to liken it to what Mr. G. W. Butler 

 has termed the " post-hepatic septum " in the Teiidae. This 

 structure, with which I am perfectly familiar from my own 

 dissections, is a transverse septum which is attached to the ventral 

 parietes, and nearly completely shuts oS the liver-lobes from the 

 rest of the abdominal cavity. In the Iguanidae (Iguana, Metopoceros, 

 Phrynosoma) there is apparently a trace of this post-hepatio 

 septum in the shape of a membrane of limited extent which arises 

 from the end of the right lobe of the liver, and is attached to the 

 lateral parietes, forming thus a pocket shutting off the lung 

 of that side of the body. In the Crocodile the membrane 

 covering the liver, which represents a portion of the oblique septa, 

 is reflected below the liver and separates it from the adjacent 

 stomach ; this is probably to be also looked upon as a repre- 

 sentative of the structures mentioned. 



5. A Note upon Dissura episcopus, with Remarks upon the 

 Classification of the Herodiones. By Frank E. 

 Beddard, M.A., F.R.S., Prosector to the Society, 

 Examiner in Zoology and Comparative Anatomy to 

 the University of London. 



[Eeceived January 13, 1896.] 



As is well known, one of the main points of difference between 

 the Ciconiidae and the Ardeidse is that the former possess the 

 ambiens muscle, while the latter do not. But the late Prof. Garrod 

 pointed out to this Society ' some years since that this general rule 

 is not without exceptions ; for in Xenorhyncfius senegalensis and 

 Abdimia sphenorhyncha he discovered that the muscle so typical of 

 the Storks was absent. Another point of difference between the 

 Storks and the Herons is in the structure of the syrinx ; in the 

 Storks this modified region of the windpipe curiously resembles 

 the syrinx of the tracheophone Passeres, while the Herons have a 

 perfectly typical tracheo-bronchial syrinx. I found myself some 

 years ago^ that Xenorhynclms senegalensis, and more especially 

 Abdimia spJienorhyncha, offered some points of likeness to the 

 Herons in the structure of their syringes, which appeared to me 

 to have some significance when correlated with the muscular 

 peculiarity already referred to. In Abdimia (cf. fig. 2, p. 233), 



' "Note on an Anatomical Peculiarity in certain Storks," P. Z. S. 1877, p. 711. 

 a "On the Syrinx in certain Storks,""?. Z. S. 1886, p. 321. 



