88 
ILLINOIS BIOLOGICAL MONOGRAPHS [88 
EXPLANATION OF PLATE 
. 64.—Transverse section through the planum basale of Necturus maculatus 30 mm. long. 
. 65.—Transverse section through the posterior part of the fenestrated process of Necturus 
maculatus 45 mm. long. 
. 66.—Transverse section through the planum verticale of the younger larva of Epicrium 
glutinosum, 
ig. 67.—Transverse section through the same region of a 90 mm. Epicrium. 
ig. 68.—Transverse section through the planum basale of the same animal. 
Fig. 69.—Transverse section through the planum verticale of the older Amphiuma means larva 
Fig. 70.—Transverse section anterior to the planum verticale of Amphiuma means 82 mm. 
long. 
Fig. 71.—Transverse section through the planum basale of the same animal. 
Fig. 72.—Transverse section through the anterior planum basale of a larva of Pipa americana. 
Fig. 73.—Transverse section slightly posterior to the above. 
Fig. 74.—Transverse section through planum verticale of Pipa americana. 
Fig. 75.—Transverse section through the choanal region of Pipa americana. 
Fig. 76.—Transverse section through the external naris of Hyla pickeringii. 
al p alary process al olfactory lobe 
anc alinasal cartilage on olfactory nerve 
ce columna ethmoidalis ond dorsal root of olfactory nerve 
ch choana onv ventral root of olfactory nerve 
ct cornu trabeculae oo — optic organ 
€ ethmoid bone ? profundus branch of the fifth nerve 
en external naris pb planum basale 
eng external nasal glands pf — prefrontal 
fen nb fenestra naso-basalis pm premaxillary 
fen pr fenestrated process pp pterygoid process 
fr frontal ps parasphenoid 
tg intermaxillary gland pt  planum tectale 
jo organ of Jacobson ~v _ planum verticale 
le lamina externa s superficialis of the fifth nerve 
m maxillary bone spc superior prenasal cartilage 
n nasal bone v vomer 
7) nasal organ 
0c oblique cartilage 
