280 



ZELENY. 



[VOL. II. 



PLATE IV. 



MB. 



HB. 



Ht. 



FIG. 6 (PI. IV), Stage E. Median sagittal section of Chelydra serpentina. 



Lg. = 7 mm. X 50. 



MB.- 



Hyp. 



FB 



KB. 



Frc. 7 (PI. IV), Stage F. Median sagittal section of A. spinifer. 

 Lg. = 7.5 mm. x 50. 



