
No. 458.] REPTILIAN LOWER JAW. 61 
Later this element fuses with the bone ossifying in the posterior 
end of the meckelian, thus forming a part of the articulare, 
which, as is well known, consists of both cartilage and dermal 
constituents in the Lacertilia. For this dermal element, which 
in some reptiles is distinct throughout life, I have adopted the 
term dermarticulare.! Its characteristics are its position on the 
posterior inner side of Meckel's cartilage, its inferior margin 
being overlapped by the angulare and its anterior end, which 
lies ventral to the coronoid, by the splenial element next to 
be described. 
The angulare (az) lies on the ventral surface of Meckel's 
cartilage, its posterior end reaching to about the middle of the 
dermarticulare, the lower margin of which it overlaps. The 
splenial (s) lies on the inner surface of the meckelian, its pos- 
terior end overlapping the anterior end of the dermarticulare. 
The coronoid (c), which lies on the inner side of the jaw dorsal 
to the splenial and the anterior end of the dermarticulare, needs 
little description. 
On the outer side of the jaw are the dentary and the sur- 
angular bones. The dentary (4) occupies the anterior two 
thirds of the jaw, bending below the meckelian so as to be visible 
beneath it from the inner side, while above, it makes a broad 
in-curved and down-curved plate, the future alveolar surface. 
The surangular (sa) lies in the posterior third of the jaw, 
extending backwards behind the articulation but not quite to the 
posterior end of the meckelian, while below it hardly reaches the 
ventral border. Its upper margin arches in a broad curve above 
the meckelian from which it is separated by a large space. 
The changes involved in the future development are exten- 
sions of allthe bones so that the meckelian is covered on both 
inner and outer surfaces and in the coössification of articulare 
and dermarticulare to a single element (Figs. 2, 2a). It will be 
seen that these parts agree in names and positions with those 
described by Cuvier. The only difference between his account 
and that given here is the recognition of the dermarticulare as a 
! This term has been used in the ganoids by van Wijhe. In some instances 
the element he has so called is clearly homologous with the dermarticulare of the 
reptiles but in others (Amia) it is a different form. 
