640 MR. W. F. R. WELDON ON THE [DeC. 1 8, 



the rest are hidden by a thick horizontal septum of connective tissue 

 stretching across the whole body-cavity from the pericardium to the 

 cloaca. The attachments of this septum are, anteriorly, to the 

 posterior margin of the pericardium ; laterally, to the side walls of 

 the abdomen, just ventral to the line of attachment of the oblique 

 septum ; and posteriorly, to the body-wall just ventral to the 

 anus. 



The liver is, as has been said, entirely ventral to this septum, 

 ■while the stomach perforates it. 



The iimhilical ligament is converted into a strong vertical septum, 

 running between the lobes of the liver, and extending anteriorly to 

 the pericardium, posteriorly to the middle of the gizzard (fig. 6, v. 

 Sep.). 



This arrangement of septa is found in all the Storks I have dis- 

 sected \ and is exactly repeated in Phoenicopterus, while I have not 

 found it in any other birds. In all the Anatidse, for example, the 

 representative of the horizontal septum is attached to the ventral 

 abdominal wall, almost immediately behind the liver, so that it does 

 not cover any of the intestinal coils ^. 



The arrangement above described is associated, both in Phceni- 

 copterus and the Storks, with a peculiarity in the air-cells themselves. 



The pulmonary aponeurosis^ is not muscular. 



The prcebronc/iial air-cells vary greatly in size, and are divided 

 by a complicated arrangement of transverse septa into smaller cham- 

 bers ; in LeiHoptilus there are five such chambers in each cell, in 

 Phoenicopterus four. This divided condition is not dependent on 

 the size of the cells, because in Phoenicopterus, where they are small 

 and deeply buried among the muscles of the neck, the dividing 

 Fepta are as well developed as in the Adjutant, where each air-cell 

 extends nearly a third of the way up the neck. 



The suhbronchial cells are completely fused, no trace of the original 

 partition remaining. The fused cells project forwards between the 

 clavicles, from which a small horizontal septum projects, partially 

 dividing a prseclavicular from a postclavicular portion. 



The prseclavicular portion is compressed by a muscle, which 

 radiates over its outer surface from the clavicle. 



The anterior and posterior intermediate cells present nothing 

 remarkable, their relations being sufficiently shown. Indeed the 

 condition of these cells seems, so far as I have been able to ascertain, 

 to be singularly constant in all birds. 



The abdominal cells are very large, extending to the extreme end 

 of the body. The obhque septum, in the abdominal region, is 

 attached to the vertebrae very near the middle line ; passing ventral- 

 wards, the two septa diverge, forming a chamber iu which lie the 



1 Lcjiioptilus argala anA javanicus ; Ciconia nigra and. C.maguari; Mycteria 

 americana ; Tantalus sp. ? ; Carphibis spinicolhs ; Xenorhynchus senegalensis. 



^ This septum has been mentioned by various authors ; but, so far as I am 

 aware, no special name has been applied to it. From its resemblance to a 

 modified Mammalian mesentei-y, I would propose to call it " pseudepiploon.^' 



3 For ail explanation of the terms used in describing air-cells, see Huxley, 

 " On the Kespiratory Organs of Apteryx," P. Z. S. 1882, p. 560 et seq. 



