206 Charles Searing Mead. 



of the ethmotiirbinals to be developed and is the only one present 

 at this embryonic stage. It springs from the lateral wall of the 

 cavity a short distance behind the outer angle of the fenestra cribrosa 

 and extends diagonally forward and inward halfway to the nasal 

 septum. The recessus posterior thus forms a space shaped like 

 the half of a cone with the base against the ethmoturbinal process, 

 the flat side along the septum, and the apex in the posterior end of 

 the nasal capsule. 



The recessus laterale is divided by a horizontal shelf into a 

 recessus laterale superior and a recessus laterale inferior (Voit). 

 It is the large size of these that causes the prominent swelling on 

 the side of the nasal capsule. The recessus laterale superior is oval 

 in shape and lies in the highest part of the capsule. The recessus 

 laterale inferior lies in the lower part of the capsule, posterior to the 

 lower arm of the nasoturbinal. Posteriorly it is continued beneath 

 the recessus posterior into a narrow cavity, the sinus maxillaris 

 (Yoit), which lies median to the processus maxillaris posterior. Of 

 the finely developed ethmoturbinal system of the adult, there is as 

 yet no indication. 



But little has been said in this paper about the membrane bones. 

 At this stage they are relatively unimportant. The larger ones, the 

 premaxilla, maxilla, vomer, palatine, frontal, parietal and dentary, 

 have already started to fo'rm, while the smaller ones, the nasal, 

 lacrymal, jugal squamosal, tympanic and goniale, are as yet un- 

 ossified. 



Conclusions. 



The principal results obtained from this study of the chondro- 

 cranium of the pig may be summarized briefly as follows : 



The planum basale is broad and plate-like posteriorly, while in 

 its anterior half it has been compressed from side to side by the 

 large cochlear portions of the ear-capsules. 



The occipital condyles are of the typical double mammalian type. 

 The two synovial sacs surrounding the condyles are separate in 

 most mammals, but in Sus they unite across the median line. 



Instead of lying above the basal plate, as in Echidna, or passing 

 continuously through this, as in most mammals, the notochord, near 



