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Show 1896.] MR. F. E. BEDDARD ON DI8SURA EPISCOPUS. 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 Teiidse. This structure, with which I am perfectly familiar from m y own dissections, is a transverse septum which is attached to the ventral parietes, and nearly completely shuts off the liver-lobes from the rest of the abdominal cavity. In the Iguanidse (Iguana, Metopoceros, Phrynosoma) there is apparently a trace of this post-hepatic 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 representative of the structures mentioned. 5. A Note upon Dissura episcopus, with Remarks upon the Classification of the Herodiones. By F R A N K E. B E D D A R D , M.A., F.R.S., Prosector to the Society, Examiner in Zoology and Comparative Anatomy to the University of London. [Received January 13, 1896.] As is well known, one of the main points of difference between the Ciconiidae and the Ardeida? is that the former possess the ambiens muscle, while the latter do not. But the late Prof. Garrod pointed out to this Society1 some years since that this general rule is not without exceptions; for in Xenorhynchus 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 ago2 that Xenorhynchus senegalensis, and more especially Abdimia sphenorhyncha, offered some points of likeness to the Herons in the structure of their syringes, which appeared to m e to have some significance when correlated with the muscular peculiarity already referred to. In Abdimia (cf. fig. 2, p. 233), 1 "Note on an Anatomical Peculiarity in certain Storks," P. Z. S. 1877, p. 711. 8 " O n the Syrinx in certain Storks," P. Z. S. 1886, p. 321. |
