Forebrain and Midbrain of Lizards 
21 
parallelism between the agamids and 
iguanids since terrestrial taxa of both fami- 
lies possess a well-developed lateral cortex. 
In contrast to gekkonids, lacertids, and 
scincids, the agamids, chamaeleonids, and 
iguanids all possess a small nucleus 
sphericus. In some agamids and all chamae- 
leonids that I have examined, nucleus 
sphericus is so reduced that it cannot be 
identified with certainty and will require 
experimental verification. The teiids, helo- 
dermatids, and varanids possess hyper- 
trophied accessory olfactory bulbs, and nu- 
cleus sphericus in these taxa shows a num- 
ber of specializations. In Heloderma, this 
nucleus enlarges until it occupies the entire 
length of the dorsal ventricular ridge and 
actually forms a second ridge rostrally over- 
lying the dorsal ventricular ridge (Fig. 6). 
In many varanids this same nucleus is again 
so large that the cell plate is thrown into 
folds giving the nucleus a laminated appear- 
ance when seen in cross section (Fig. 7). 
Clearly the range of variation of the 
vomeronasal system in lizards is so great 
that they are an ideal group to examine the 
possible role of this chemo-system in feed- 
ing, territorial, and reproductive behaviors. 
Figure 6. Camera lucida drawings of transverse sections through the right telencephalic hemisphere of 
Heloderma (A-C) and Lanthanotus (D-E). Bar scale represents 2 mm. cd, dorsal cortex; cm, medial cor- 
tex; cn, central or core nucleus of dorsal ventricular ridge; d, diencephalon; dvr,a,p, anterior and posterior 
divisions of the dorsal ventricular ridge; Is, lateral septal nucleus; ms, medial septal nucleus; na, nucleus 
accumbens; ns, nucleus sphericus; ot, olfactory tubercle; st, striatum; vm, nucleus ventromedialis. 
