PRE- AND POSTOPERATIVE PERFORMANCE ON THE VISUAL CLIFF AND IN THE OPTOKINETIC DRUM WERE COMPARED FOR TURTLES WITH BILATERAL CORTICAL, TECTAL, AND COMBINED CORTICAL-TECTAL LESIONS. COMBINED LESIONS PRODUCED A SIGNIFICANT PERFORMANCE DEFICIT. LESIONS OF THE CORTEX OR TECTUM ALONE, HOWEVER, DID NOT SIGNIFICANTLY ALTER PERFORMANCE ON THESE TASKS. THESE RESULTS INDICATE THAT THE REPTILIAN GENERAL CORTEX IS OF FUNCTIONAL IMPORTANCE FOR THE PERFORMANCE OF SIMPLE, VISUALLY GUIDED TASKS. (PsycINFO Database Record (c) 2006 APA, all rights reserved)