86 ILLINOIS BIOLOGICAL MONOGRAPHS [86 



EXPLANATION OF PLATE 



Fig. 53. — ^Transverse section through the foramen olfactorius of Diemictylus viridescens 38 mm. 

 long. 



Fig. 54. — ^Transverse section through the anterior part of the nasal organ of the same animal. 



Fig. 55. — ^Transverse section through the foramen olfactorius of the adult Diemictylus virides- 

 cens. 



Fig. 56. — Transverse section through the pons ethmoidalis of Triton cristatus 28 mm. long. 



Fig. 57. — Transverse section through the planum basale of Triton cristatus 35 mm, long. 



Fig. 58. — Transverse section through the planum basale of Cryptobranchus alleghaniensis five 

 weeks old. 



Fig. 59. — ^Transverse section through the anterior end of the nasal organs of Spelerpes bilinea- 

 tus 15 mm. long. 



Fig. 60. — ^Transverse section just anterior to the planum basale of Spelerpes bilineatus 37 mm. 

 long. 



Fig. 61. — Transverse section through the same region of Spelerpes bilineatus 46 mm. long. 



Fig. 62. — Transverse section through the choanal region of Pletkodon erytkronotus adult. 



Fig. 63. — Transverse section through the lamina medialis of the same animaL 



no nasal organ 



el olfactory lobe 



on olfactory nerve 



00 optic organ 



p profundus of the fifth nerve 



pb planum basale 



pe pons ethmoidalis 



pm premaxiUary bone 



pi planum tectale 



pv planum verticale 



s superficialis of the fifth nerve 



t trabecula 



