CHONDROCRANIUM OF EUMECES 189 
12 b) and crocodiles (Shiino, 714), in correlation with the general 
completeness of the ethmoid region; on the other hand, in 
Vipera (Peyer, 712) it is merely suggested in the procartilage 
stage, and the continuity is soon interrupted. 
In the posterior third of the ethmoid region the paries nasi is 
most extensive and, at the same time, most complicated, owing 
to the formation of a great lateral bulb (fig. 2, p.eat.), housing 
the extraconchal recess of the nasal cavity. This extraconchal 
part of the nasal capsule, as already noted, extends forward as 
well as laterally, so that it comes to lie in part at the side of the 
middle third of the capsule. From this it is separated by the 
conchal infolding (fig. 2, co.) and its anterior opening, the aditus 
conchae (fig. 1, ad.co.). The concha (fig. 26, co.) has the form 
of an inverted trough, extending obliquely from anterodorsal 
to posteroventral, and is open, in this stage, not only at the 
anterior end, but also ventrally throughout its entire length. 
At its posterior end the trough is terminated by the bending 
together of its lateral, dorsal, and medial walls. On one side 
of the specimen modeled this posterior closure is incomplete. 
Conditions have not materially changed in stage 6, but, in 
still later stages, it may well be that the concha becomes defi- 
nitely tubular through the closure of the posterior part of its 
ventral opening, as described in the later development of Lacerta. 
Lateral to the concha the paries nasi is so modified that it forms 
not only the lateral wall, but also a roof, a floor, and a partial 
median wall for the extraconchal recess (fig. 26); in the region 
of the aditus conchae, as may be seen from figures 1 and 2, the 
section of the extraconchal portion of the nasal capsule would be 
a closed circle. Behind the concha (fig. 25), the paries nasi again 
takes on a simple configuration. A concha similar to that- of 
the lizards is described in Vipera by Peyer (12) and Crocodilus 
by Shiino (14); in the turtles it is rudimentary (Gaupp, ’05 b; 
Nick, 712; Kunkel, ’12 b). 
In a discussion of the mechanical origin of the concha, Gaupp 
(700) cites the view of Seydel (’95, ’96), who interprets the external 
nasal gland as an active factor, pushing in the capsular cartilage, 
and thus separating off the extraconchal recess. Gaupp himself 
