60 THE AMERICAN NATURALIST. [Vor. XXXIX. 
the operculum of fishes, while for the complementaire he 
adopted the alternative coronoid because of its resemblance 
to the earlier named coronoid process of the mammalian jaw. 
Other names have been changed by other authors.! Thus Wag- 
ner calls the articulare the pars angularis, the dentary the pars 
alveolaris,the angulare the 5. complementaris posterior, the sple- 
nial the 2. comp. anterior, and the surangular the 5. comp. exterior, 
while Brühl calls the splenial the marginale ; the surangular and 
the coronoid, the ecto- and endo-complementare. Baur (Anat. 
Anz., xi, 1896) has attempted to homologize these bones in dif- 
ferent reptiles, but it would seem that he has fallen into one or 
two errors, by taking the turtle rather than the crocodile or the 
lizard as his basis. As will be seen below there is practical uni- 
son in the use of terms by Cuvier in both crocodile and lizard 
while the turtle exhibits some differences, and again, to use the 
turtle as the basis would introduce no little confusion into the 
literature. So I have adopted the lizard as the basis of my 
work. 
Practically all authors are agreed upon two of the elements, 
the dentary and the articulare, the first forming the anterior 
bone of the lower jaw, the latter being developed by ossification 
in the posterior part of Meckel’s cartilage and forming a bone 
by which the lower jaw is articulated with the quadrate. 
In an embryo of the lizard Sceloporus in which the centers of 
ossification have appeared, reconstruction from serial sections 
shows the following elements (Fig. 1). Meckel's cartilage (zz) 
is a long, slender, slightly curved cylindrical rod, the cartilages 
of the two sides being continuous at the symphysis of the jaw. 
Just in front of the articulation with the quadrate, a strong dor- 
sal process marks the anterior boundary of the articular facet 
(4), the cartilage extending a short distance behind this point. 
The most posterior ossification is a long and slender bone 
(da) which extends backwards nearly to the posterior end of 
the meckelian. Behind, it lies on the lower inner surface of 
the cartilage, but farther forward it rises on the inner surface. 
: ‘No attempt has been made to find all the terms employed, or to trace each to 
its earliest use. 
