THE TELENCEPHALON IN CYCLOSTOMES 379 
vent. III 
Fig. 8 Petromyzondorsatus, ammocoetes. Model of the dorsal portion of the 
left half of the forebrain, drawn as seen from the medio-ventro-caudal direction. 
The model was carefully constructed on a large scale in order to determine whether 
the velum transversum really formed a continuous fold from the median line to 
the lateral attachment of the tela (i. e., the taenia). This drawing should be com- 
pared with figures 23 to 27. d.m.c., dorsal sac. 
