55] THE NASAL ORGAN IN AMPHIBIA—HIGGINS 55 
jally into a small superior prenasal process which extends ventrally and 
medially from the capsule. The inferior prenasal process is considerably 
longer than the superior; it arises from the planum basale just in front of 
the choanal gap and extends forwards and downwards into the internasal 
space (Fig. 78). Forming the floor of the c. medium, and extending back- 
ward beneath and slightly lateral to the lamina externa is a conical process 
considerably larger than that in Bufo; the possible remrfant of the original 
cornu trabeculae. 
Two small foramina pierce the solum anterius; the smaller and more 
dorsal conducts the nasalis internus from the capsule, while the larger more 
medial one is the fenestra naso-basalis, considerably smaller than that 
described for Bufo. 
RANA VIRIDESCENS 
The nasal capsules of the Arcifera and the Firmisternia are essentially 
alike, and, although I lack a series of stages showing the chondrification of 
the nasal capsule in Rana, the work of Gaupp (1893) has made it possible 
to compare the growth of the nasal capsule of the frog in connection with 
my own two stages. 
In a larva 28 mm. long (entire length), in which the characteristic 
Anuran chondrocranium is beginning to develop, the nasal capsule (Fig. 40) 
consists of an elongate planum basale (pb), with the anterior extension of 
the trabeculae to the labial cartilages. The muscularis process of the 
quadrate (mpq) has fused with the lateral wall of the planum basale, and 
just above the junction of the two a dorsal process has arisen from the 
basale, which is to become the side wall of the capsule (Fig. 83). Gaupp 
(1893) has referred to this cartilage as the ‘“‘Ethmoidal-pfeiler,” but it 
differs from the ethmoidal column of Amblystoma in which chondrification 
of this bar is independent of the planum basale. 
Medial processes from the dorsal margin of each columna ethmoidalis 
fuse in the middle line and form a pons (fe), recalling this same structure 
in Amblystoma and in Salamandra (Fig. 84). In all three genera the 
cavum cranii and the nasal cavity are continuous during a part of the 
larval development by means of the fenestra ethmoidalis (fen eth) ventral 
to the pons. Unlike Triton and Diemictylus however, chondrification 
from the pons to the planum basale soon develops the ethmoidal wall which 
separates these cavities. 
Upon a level with the pons ethmoidalis, and arising from the dorsal 
part of the ethmoidal column, a small process extends laterally toward the 
muscularis process of the quadrate. A small opening, which must be 
regarded as the foramen orbito-nasalis for the nasalis internus nerve, 
pierces this process near its base; and from this identification, it follows 
that this process must contain parts of both planum tectale and processus 
antorbitalis, the latter being beneath the foramen. The more dorsal posi- 
