570 MR. J. B. SUTTON ON THE CRANIAL ARCADE. [Dec. 2, 



If the orbital surface be next examined, the infraorbital groove will 

 be found unclosed even at birth on the facial surface of the maxilla, 

 the two sides not having united to form the canal for the transmission 

 of the infraorbital nerve. This groove is an excellent landmark, for all 

 that portion lying to its outer side arises from a distinct centre, 

 whereas that part which lies between the groove and the palatal 

 portion arises also from an independent ossific nucleus. The outer 

 nucleus will be referred to as the " malar " portion, whereas the inner 

 piece, constituting as it does the main mass of the bone and being 

 hollowed out subsequently to form the antrum, will be termed the 

 maxillary centre ; at the time of birth it is a solid mass of bone with 

 a shallow groove on its inner aspect. 



It now is evident that for morphological purposes the superior 

 maxilla consists of four distinct portions : — 

 («) The premaxillary region in relation with the ethmo-vomerine 



cartilage and the naso-palatine nerve. 

 (6) A pre-palatine portion forming a platform for the support of 

 the anterior end of the vomer. 



(c) A maxillary centre situate to the inner side of the superior 



maxillary division of the fifth nerve. 



(d) The malar piece, lying outside this nerve and supporting the 



malar bone. 



The relations these various centres bear to one another are shown 

 in fig. 1. 



Now comes the task of selecting the centre in Man's maxillae cor- 

 responding to the Pike's vomer, so called. Careful comparison of 

 the two skulls convinces me that the "pre-palatine" centres of the 

 mammalian maxillae represent the piscine vomerine bones, for the 

 following reasons : — 



(1) They are membrane-formed bones. 



(2) The bone in each case underlies the anterior end of the vomer 



and parasphenoid respectively. 



(3) Although in the Pike the so-called vomer is median and single, 



nevertheless in Lepidosteus, Rana, Menobranchus, and many 

 other forms the bones so named are double. 



(4) In their relation to the premaxillae aud palate bones they fulfil 



the required anatomical conditions. 



In order to bring out these facts with greater clearness I have 

 arranged side by side in Plates LIII. & LIV. figs. .5-8 the corre- 

 sponding regions in a fish {Lepidosteus), in a Lizard {Lacerta ucjilis), 

 in a Wombat (Phascolomys), and in a human foetus at birth. It will 

 be at once evident that the bones lying behind the premaxilla are 

 totally different in their surroundings from the vomer of mammals, 

 whereas there is a very close and accurate agreement if they be 

 considered as the pre-palatal portion of the superior maxilla of 

 mammalian anatomy. 



A careful survey of these facts must convince any impartial 

 anatomist that the bones in Fish and Amphibians usually denominated 

 " vomers" must part with their claims to that title and yield it to 

 the so-called parasphenoid. It now becomes necessary to find a 



