92 OSBORN. (Vou. II. 
EXPLANATION OF PLATE IV. 
The figures of the brains were outlined with a Nachét camera lucida, and the sur- 
face details inserted as studied in different lights. The vertical sections (Figs. 7-9) 
are reconstructions of the actual median plane by composition of a number of sec- 
tions. 
FicurE 1. Brain of Sivredon (Axolotl) mexicanus. The species is somewhat 
uncertain. Viewed from above. Enlarged 4} diameters. 
Fic. 2. Brain of Mecturus (Aenobranchus) maculosus. Viewed from above. 
Enlarged 45 diameters. 
Fics. 3 AND 4. Brain of Proteus anguineus. Viewed from below and above. 
Enlarged 43 diameters. 
Fic. 5. Brain of Siren lacertina. Viewed from above. Enlarged 4} diameters. 
Fic. 6. Medulla oblongata of Cryptobranchus alleghaniensis. Viewed upon the 
ventral surface, showing the exit of the cranial nerves, as reconstructed from trans- 
verse sections. 
Fic. 7. Sagittal section of the brain of Cryptobranchus, through an ideal median 
plane, as reconstructed from sagittal sections. 
Fic. 8. Sagittal section of the brain of Mectwrus, drawn as above. 
Fic. 9. Sagittal section of the brain of ana, drawn as above. 
