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Show 570 MR. J. B. SUTTON ON THE CRANIAL ARCADE. [Dec. 2, If the orbital surface be next examined, the infraorbital groove 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 :- (a) The premaxillary region in relation with the ethmo-vomerine cartilage and the naso-palatine nerve. (b) 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 corresponding 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, Bana, Menobranchus, and many other forms '* e bones so named are double. (4) In their relation to the premaxillae and 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 corresponding regions in a fish (Lepidosteus), in a Lizard (Lacerta agilis), 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 |