18 WILLIAM K. GREGORY 
Operculare Cuvier (splenial Owen): on the inner side of the 
jaw, opposite the dentary, articulating posteriorly with com- 
plementare (coronoid) goniale and angulare. Absent in most 
Cryptodira and certain other Chelonia: tooth-bearing in certain 
recent Amphibia. Wrongly named presplenial by Baur in 
lizards and crocodiles. 
Complementare Cuvier (coronoid Owen): lying chiefly on the 
inner side, between the supraangular and operculare (splenial). 
Not present in recent Amphibia. 
These elements in recent reptiles and Amphibia are very loses 
illustrated in the fine series of figures published by Gaupp‘ 
representing embryonic and adult conditions. 
The critical element for the understanding of the lower jaw 
of recent reptiles and amphibians is the goniale. This element 
was recognized by Baur (’95) in the lizard as a ‘dermogenous’ 
process of the articular, but he greatly confused the subject by 
calling the same element in the turtles the ‘angular,’ by apply- 
ing to the true or Cuvierian angular the name ‘splenial’ and by 
renaming the true splenial ‘presplenial.’ This strange blunder 
was set right at last by Williston (’03), Kingsley (’05) and Gaupp. 
The recognition of the goniale as an element distinct both from 
the articular and the angular is of great importance, not only 
in clearing up the morphological relations of these elements in 
amphibians and reptiles, but also in bringing additional evidence 
for ‘Reichert’s theory’ of the origin of the mammalian auditory 
ossicles (see p. 23). 
MAMMALIAN LOWER JAW 
From the side of ‘neontology’ (embryology plus comparative 
anatomy) the manifold evidence bearing on the origin and mor- 
phological relationships of the mammalian lower jaw has been 
ably arranged by Gaupp (1911, III) in favor of the following 
conclusions: 
1. The mammalian mandible is the homologue solely of the 
reptilian dentary bone. The ascending ramus including the coro- 
41911, pp. 104-117, figs. 5-16; pp. 487-455, figs. 1-23. 
