CHONDROCRANIUM OF EUMECES 195 
Lacerta, it is set obliquely, with one face turned upward and 
outward, the other inward and downward (figs. 25 and 26, c.par.). 
In Eumeces (fig. 2) the paraseptal cartilage forms independently 
of the capsule of Jacobson’s organ, and is widely separated from 
it in the earlier embryos; during development the gap is gradually 
lessened and, in stage 6, is entirely closed on one side, while the 
interruption on the other side is very slight. Thus conditions 
become essentially as described for Lacerta. Kunkel (712 b) 
notes that the union of the paraseptals with the planum antor- 
bitale occurs at a very late stage in the development of Emys. 
In Eumeces both cartilages, especially the planum antorbitale, 
are of relatively late development and difficult to distinguish 
in younger embryos, but there is no evidence for an original 
separation and later fusion. 
The forward half of Jacobson’s organ, as stated, is supported ° 
by the cartilaginous capsule; behind this the organ has no carti- 
laginous support. But this deficiency is supplied by the large 
trough-like vomer (fig. 2, os vo.), which underlies the rudimentary 
solum nasi (figs. 27 and 28), and, behind it (figs. 25 and 26), 
takes its place as a support for Jacobson’s organ and as a floor 
for the whole capsule. The vomer extends back almost to the 
planum antorbitale, where its place is taken by the palatine 
(fig. 2, os pal.). Jacobson’s organ is also roofed over and sepa- 
rated from the nasal cavity proper by another membrane bone, 
the septomaxillary (figs. 27 and 28, os s-mazx.), which forms an 
inverted saucer with its median edge supported by the septum, 
its lateral edge by the solum and the maxillary bone. In length 
it is practically coextensive with Jacobson’s organ, to which its 
functional relation is very apparent. 
The floor of the extraconchal recess is really a part of the 
complexly folded paries nasi, and has been noted already in that 
connection. 
The reptiles show a wide range of variation in the nasal floor 
as in other parts of the ethmoid region. The floor is highly 
developed in Crocodilus (Gaupp, ’05b; Shiino, ’14) and the 
turtles (Nick, 712; Kunkel, ’12 b), although exceptionally variable 
in the latter group. In snakes it is very rudimentary. In the 
