502 



SLONAKER. 



EXPLANATION OF PLATE XXXL 



The following figures were made from sections through the whole head with 

 eyes in situ. FN marks the axis of vision for the fovea nasalis ; FT, fovea tem- 

 poralis ; and Op, the entrance of the optic nerve indicated by the pecten. 



The slight divergence of the lines of binocular vision {FT) is probably due to 

 the relaxation of the internal recti muscles after death. 



Fig. 64. White-Bellied Swallow (Tachycineta bicolor), \. 



Fig. 65. Common Tern (Sterna hirundo), \. 



Fig. 66. Sparrow Hawk (Falco sparverius), \. 



Fig. 67. Broad-Winged Hawk (Buteo latissimus), \. 



Fig. 68. Great Horned Owl (Bubo virginianus), |. 



