CHONDROCRANIUM OF EUMECES INPEFE 
the taenia parietalis media stops at this point, but in this early 
embryo of Eumeces it can be clearly traced backward and up- 
ward to a union with the taenia marginalis, as figured. Thus 
the fenestra prootica is divided into two fenestrae—an antero- 
dorsal and a posteroventral, designated respectively as fenestra 
prootica superior (fen.pr-ot.s.) and fenestra prootica inferior 
(fen.pr-ot.i.). A further addition to the skeletal plan of Lacerta 
is seen in the bar, marked 2 in the figure, which again subdivides 
the fenestra prootica superior. This bar is exceedingly thin 
and of rather questionable structure; it 1s not deemed worthy 
of aspecial name. The scanty development of the taenia margi- 
-nalis in this stage leaves the fenestra prootica inferior and the 
fenestra epioptica (fen.e-op.) dorsally incomplete. 
From the same diagram it is easy to trace the probable hom- 
ology of the cartilage spur projecting posteriorly from the junc- 
tion of subiculum infundibuli and taenia parietalis media in 
stage 5, as well as the isolated fragment near its tip. The rep- 
resentation of stage 5 in this figure is not exact nor drawn to 
scale; all portions common to the two stages are represented 
as in stage 2, but the relation to nerve exits makes possible a 
close approximation to accuracy as regards the two cartilages 
under consideration. Both belong to the taenia parietalis media, 
the isolated fragment falling wholly or mainly in the posterior 
extension (t.par.m’.) which is lacking in Lacerta. 
Of especial interest in this comparison of earlier and later 
stages of Eumeces is the fact that different parts of the lateral 
wall show very diverse degrees of development. For the most 
part, the latticework is more complete in the younger embryos. 
But, while the major part of the lateral wall in stage 5 has suf- 
fered a marked ontogenetic regression, the taenia marginalis is 
still developing progressively and has only just reached its com- 
plete extension. An exactly parallel progressive development 
of the taenia marginalis after other portions of the temporal wall 
are already in regression is shown in the figures of Sphenodon 
by Howes and Swinnerton (’01).. These observations may well 
have considerable phylogenetic significance in comparison with 
the Mammalia. Here the commissura orbitoparietalis, which is 
