104 BG. Wilder—Anterior brain-mass with Sharks and Skates 
prosencephalon,” I was led to conclude that the small hollow 
bud from the side of the anterior brain-mass (evidently the 
slightly modified anterior cerebral vesicle) of the foetal Mustelus 
must elongate and expand at its tip in contact with the olfac- 
tory sack so as to form the lobe and crus; page 182. But the 
young and adult brains since examined show that the ventricle 
ends as a rounded cul-de-sac before reaching the “lobe.” The 
is the case in Acanthias and others with short “ crura.” 
b . 
usually inward within the lateral masses separated by the 
