^yS DAVISON. [Vol. XI. 



dorsal wedge of the premaxillary, and the union of the de- 

 scending plates at this point functions as a nasal septum, as 

 seen in Fig. III. Through this portion of the bone is the canal 

 for the passage of the olfactory nerve. Hay (2) does not believe 

 that such a canal exists, though Wiedersheim (i) has correctly 

 described it. Cope (4) has called the descending union of the 

 frontals the ethmoid. In this he is wrong, as embryonic in- 

 vestigations (3) have clearly shown, I think the Sarasins (9) 

 have followed Cope in this error, and together with him have 

 sought to show relationships which do not exist. The frontals 

 are in contact with the nasals and premaxillaries anteriorly, 

 and laterally join the prefrontals and orbitosphenoids. Upon 

 reaching the frontal bone the sagittal crest of the parietals 

 divides, each fork running to the outer side of the former bone. 

 In the groove thus formed lies the temporal muscle. The pre- 

 frontals take part in roofing the nasal chambers, have a rough 

 surface and an irregularly oblong outline. They join the max- 

 illaries laterally and form part of the orbit. The orbitosphe- 

 noids are small, taking part in the lateral boundaries of the 

 brain cavity. They articulate with the parietals, parasphenoid, 

 and vomero-palatines. They are almost separated from the 

 frontals by the interposition of a narrow wedge of the para- 

 sphenoids. The vomero-palatines bear the inner concentric row 

 of teeth, which number about forty-four. TJie 7iuviber of pre- 

 maxillo-maxillary teeth is never less than fifty. The number is 

 wrongly stated by Cope as thirty-one. The vomero-palatines, 

 together with the ventral wedge of the premaxillary, form the 

 roof of the mouth. This pair of bones unite anteriorly, and 

 are nowhere separated more than two millimetres from each 

 other. Their backward extent ceases slightly posteriorly to 

 the beginning of the parasphenoid. The parietals are the 

 largest bones of the skull, and form the roof of the greater 

 part of the brain cavity. Their median juncture is the sagittal 

 crest. Their external borders are deflected upwards to form 

 the temporal crests, thus giving rise to a broad groove for the 

 reception of the powerful temporal and masseter muscles. The 

 prootics and squamosals lie lateralwards of these bones, and 

 posteriorly are joined by the exoccipitals which bear the two 



