The anatomy of the brain of the bottlenose dolphin (Tursiops truncates). Rhinic lobe (rhinencephalon). I. The paleocortex

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Abstract
The bottlenose dolphin, Tursiops truncatus, lacks olfactory bulbs and peduncles as do the other members of the odontocete suborder of Cetacea. Nevertheless the dolphin as well as the other cetacean species studied possess a rhinencephalon or rhinic lobe consisting of prominent olfactory lobes and a very reduced hippocampus covered over, respectively, by small epistriatal (frontal, especially orbital lobes and insula) and huge epihippocampal (parietal, occipital and temporal lobes) Portions of the hemisphere.In the dolphin the demarcation of the rhinic lobe from each hemisphere bilaterad to it is particularly clear and consists of a continuous circular groove (rhinic cleft) composed of posterior parolfactory, anterior and posterior rhinal, rhinohippocampal, hippocampal and callosal segments. Along the trajectory of the rhinic cleft, the cytoarchitectonic demarcation of the paleocortex (olfactory lobes) and archicortex (hippocampus) from the neocortex in the border (limbus) of each hemisphere is equally clear. The rhinic lobe in Tursiops and other Cetacea so far examined thus appears to be a formation of the telencephalon whose distinctness in these species is dramatically emphasized.Topographic disposition of the cytoarchitectonic areas of the paleocortex in Tursiops, Which have not heretofore been described, has been found in this study to be essentially similar to that of other placental mammals. These areas of the paleocortical division of the rhinic lobe (Prepyriform, tubercular, diagonal and periamygdalar areas) are as easily differentiated from one another in this species as in many other mammalian forms.