pelvis by four (or two pairs of) posterior processes, and in the centrai 



line by the elongated ridges of the posterior sacral vertebra, so as to 



be immoTeably fixed to the pelvis. The posterior disk is thick, rather 



Fig. 1. 



Fig. 2. 



Fig. 3. 



Fig. 1. Side yiew of the pelvis, wlth the inside of the attached posterior disk. 

 Fig. 2. The inside of the posterior disk, showing the position of the places of 



attachment. 

 Fig. 3. The outer side of the posterior disk, shovnng the form and position of the 



perforations. 



sohd, and furnished with a marginai series of oblong perforations, 

 havingasecondseriesofsimilar but smaller perforations within them 

 in the centre, and two series of much elongated curved slits on each 

 side, near the margin, as in the figure. 



Professor Owen informs me that a somewhat similar adhesion of 

 the skeleton to the derraal system is to be observed in the Glypto- 

 don, and also in some of the fossil Armadilloes of the older strata. 



3. On the presence or absence of Air in the Bones of 

 BiRDS. By Edwards Crisp, M. D. 



As one of the objects of the founders of this Society, as expressed 

 by the Charter, was the cultivation of Physiology, and as our Com- 

 munications of late, upon this subject, have been rather scanty, I am 

 induced to submit this paper to the notice of the members, and I do 

 so with a hope that it may serve to dispel one of the many errors 

 that unfortunately encumber the science of Zoology. 



My attention was first especially directed to the investigation of 



