The accessory olfactory bulbs and the lateral telencephalic wall of the rat‐fish, Chimaera

The lateral telencephalon of Chimaera possesses several unique features but also has nuclei and fiber systems homologous with those of other sub‐mammalian vertebrates. Ventricular ridges, similar to those of reptiles, are quite evident. Accessory olfactory bulbs are associated with the dorsal and ventral parts of each olfactory bulb. These contribute to the lateral olfactory tract. The internal granular layer caudal to the olfactory and the accessory bulbs blends with the anterior olfactory nucleus. Caudal to this nuclear area, the nuclei of the rostral telencephalon are well differentiated. Nuclear areas distinguishable in the lateral hemisphere include: the primordial dorsal pallium, the primordial piriform cortex, the primordial striatal and amygdaloid nuclei, and the lateral zone of the olfactory tubercle. These areas replace dorsal, dorsolateral, ventrolateral and ventral parts of the anterior olfactory nucleus, respectively. The primordial striatum is subdivided into hyperstriatum, neostriatum, paleostriatum augmentatum and paleostriatum primitivum. The amygdaloid area has anterior, corticomedial and basolateral nuclear groups. The basolateral area is best differentiated. The hyperstriatum forms a rostral ventricular eminence; the basolateral amygdaloid nucleus is present in a larger caudal ventricular ridge. Fiber tracts of the lateral wall include the lateral olfactory tract, the lateral corticohabenular tract, the lateral forebrain bundle and the stria terminalis. Nuclei of medial and lateral walls are interrelated through the hippocampal and the anterior commissures.