150 EDWARD L. RICE 
although opening slightly again at its extreme dorsal limit. 
This approaches closely the conditions in Eumeces. 
The fissura is divided sharply into an anteroventral recessus 
sealae tympani (fig. 8, 7.sc.ty.) and a posterior foramen jugulare 
(fig. 8, f.jug.). In Lacerta the incomplete separation is accom- 
plished by a mere narrowing of the fissure and a rather denser 
filling of connective tissue. In Eumeces the posterior ampullar 
prominence, just dorsoposterior to the fenestra cochleae, and the 
basal plate, in the region of the anterior hypoglossus foramen, 
are in very close apposition (the histological structure indicates 
that there is no absolute fusion of the cartilages), thus completely 
dividing the two parts. In stage 2 the contact is less certainly 
distinguished, owing to the embryonic nature of the tissues; in 
stages 4 and 6 the conditions are clearly as in stage 5. 
The foramen jugulare furnishes the exit for the confused mass 
of roots of nerves X and XI, and for a large vein just posterior 
to the nerves. This vein is homologized by Gaupp with the 
mammalian jugular; I have not followed its relations sufficiently 
to estimate his interpretation, but can confirm his observations. 
Conditions in the recessus scalae tympani are of especial 
interest and demand fuller consideration. Stage 5 of Kumeces 
shows a very close similarity to Lacerta. Figure 12 represents - 
a section corresponding to Gaupp’s figure 17. In the triangle 
whose apices are marked by the edge of the basal plate and the 
median and lateral rims of the fenestra cochleae is the very loose 
connective tissue in which the saccus perilymphaticus will de- 
velop, while the median and lateral apertures of the recessus 
(r.sc.ty.m. and r.sc.ty.l.) are closed by a much denser tissue, form- 
ing rather definite membranes. <A few sections further back (fig. 
11) the median aperture disappears through the approximation 
of the cartilages of otic capsule and basal plate. The membrane 
closing the lateral aperture is less developed in this region. The 
membrane closing the lateral aperture of the recessus Gaupp 
compares with the secondary tympanic membrane of the mam- 
mal, but he insists that the similarity is physiological rather 
than morphological, and that there can be no close homology 
