The evolution of the thalamocingulate division of the limbic system is identified with a family-related behavioral triad that distinguishes the transition from reptiles to mammals. In addition to contributing to the knowledge of comparative neuroanatomy, the present project was intended to aid the appropriate selection of subjects for neurobehavioral studies on functions of respective areas of the cingulate cortex. The current work focuses on the common American mole (Scalopus aquaticus) because (1) it is a member of the order of insectivores with features linking them to both mammal-like reptiles and primates; and (2) its visual deficiency is possibly associated with a poorly developed cingulate retrosplenial granular area (area 29 of M. Rose). The dimensions of a cerebral hemisphere of a mole are about 11 x 7.5 x 6 mm. Planimetric measurements of the extent of the granular cortex reveal an area of about 2.1 mm2. Further measurements of the granule cells show a range in diameter of 5 to 6.9 mu and a mean diameter of 5.8mu. There are no conspicuous differences in the distribution and cytoarchitecture of area 29 in the male and female mole. The availability of moles for this study provided the opportunity to record vocalizations. A brief description is given of a first-time, sound-spectographic analysis of several vocalizations.
