Plate VII. 



Fig. 48. Tritou cristatus, larva 36 mm. long. The section is through the 

 cephalic end of the columella where it is continuous with tlie ear capsule on 

 its medial side. 



Fig. 49. The same, farther caudad, through the columella and just in front 

 of the cephalic end of the operculum. 



Fig. 50. The same. A section still farther caudad, through the operculum 

 and back of the caudal end of the columella. Note the relations of the blood 

 vessels in this and the two preceding figures. 



Fig. 51. Cryptobranchus allegheniensis, larva 34 mm. long. The liga- 

 mentum hyo-columellare is just joining the stilus at its bend. 



Fig. 52. Crytobranchus allegheniensis. Just hatched larva. The proton of 

 the columella is seen between the artery and vein. 



Fig. 53. The same. A section farther cephalad to show the proton of the 

 squamosal connection of the columella. 



Fig. 54. Cryptobranchus allegheniensis, adult. A section through the dis- 

 tal end of the stilus to show its articulation. 



Fig. 55. The same. A section farther caudad showing the columella and 

 its large stilus illustrating the relation to artery, vein and nerve. 



