384 EDWARD PHELPS ALLIS, JR. 
process (secondary upper lip) and the side of the head, and on 
the external surface of this process (secondary lip) there is, in 
slightly older embryos (l.c., pl. 23), a shallow longitudinal de- 
pression. In still older embryos of Emys and also in those of 
Chelone (l.c., pl. 24), this depression becomes a furrow which 
lies dorsal to the ventrolateral edge of the maxillary bone, and 
hence in the position of the supralabial furrow of fishes. 
The oral nasal aperture has thus been enclosed in the buccal 
cavity without having to cut through the premaxillo-maxillary 
dental arcade, as I formerly suggested must be the case (Allis, 
00), and it even lay, primarily, aboral to the primary lip. 
Later, it cut through that lip and opened into the primary 
superior alveololabial sulcus, a median remnant of the hp ap- 
parently being left between the apertures of opposite sides and 
being represented in the choanate papilla, or papilla palatina, of 
Fuchs’s descriptions, this papilla being said by him to always 
lie, excepting in certain of the Sauria, immediately posterior to 
the primary palate, between the anterior ends of the primary 
choanae (oral nasal apertures). Having cut through this pri- 
mary upper lip and reached the primary alveololabial sulcus, 
the nasal groove encountered, in its posterior progression, the 
primary alveolar ridge, and was apparently there at first de- 
flected laterally along the external surface of that ridge, for it is 
so shown by Fuchs (’08, figs. la and 1b, pl. 61) in Hatteria, where 
the conditions are considered by him to be the most primitive 
found in the Amniota. The nasal groove, thus prolonged, evi- 
dently interfered somewhat with the free development of the 
bones in the primary dental arcade, and the groove eventually 
acquired a passage between the vomerine and palatine portions 
of that arcade and then had a sagittal course along the lateral 
edge of the body of the vomer. The continued coalescence of 
the lips of the nasal groove and the invasion of the bridge so 
formed by processes of the vomer, palatine, and maxillary, then 
gave rise to the conditions described by Fuchs in Chelone. In 
the sections of Hatteria that are given, the supralabial furrow is 
not shown, but it is shown, well developed, in the sections of 
Lacerta, and the lachrymal duct leads from this furrow to the 
primary choana. 
