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VISION 





Figure 7 Transverse sections through the right telencephalic hemisphere and olfactory 

 organ of the thornback skate, Platyrhinoidis triseriata. as, area superficialis basalis; en, 

 central nucleus; dp, dorsal pallium; fb, forebrain bundles; g, glomerular layer of olfactory 

 bulb; lp, lateral pallium; Is, lateral septal nucleus; mp, medial pallium; ms, medial septal 

 nucleus; oe, olfactory epithelium; on, olfactory nerve; pa, preoptic area; st, striatum. 



pristiophoriform, and squatinomorph sharks have a nonconvoluted corpus of 

 the cerebellum, a well-developed and dorsally exposed optic tectum, a 

 diencephalon with few migrated nuclei, and a poorly developed telen- 

 cephalon (Figures 2, 3, 9-11). This brain pattern will be referred to here as 

 the squalomorph pattern. 



In contrast, galeomorph sharks have a convoluted corpus of the cere- 

 bellum with hypertrophy leading to asymmetry in many families 

 (orectolobids, lamnids, carcharhinids, and sphyrnids), an optic tectum 



