PLATE 13 



EXPLAXAIIOX OF FIGIRES 



23 Opossum, 11 mm. H. E. C, sagittal scries, no. 925. X 20. 



24 Opossum, 2G mm. H. E. C, sagittal series, no. 2077. X 20. 



25 Rat, 9.6 mm. H. E. C, sagittal series, no. 1824. X 20. 



26 Rat, 14.4 mm. H. E. C, sagittal scries, no. 1925. X 20. 



128 



