[The work of I.I. Schmalhousen on comparative morphology of vertebrates: Significance for paleontological reconstructions (data on the seismo-sensory system of agnathans)].

The morphology and function of the seismo-sensory system of agnathans (Agnatha: Heterostraci) are analyzed. This system has been reconstructed in Cyathaspidiformes and Amphiaspidiformes. The seismo-sensory system of agnathans was compared with the lateral line system of fishes: the difference between these systems in the density of seismo-sensory lines and the contribution level of these systems to orientation in the water was detected. The possibility of reconstruction of the length and direction of heterostracans cranial nerves has been shown using the position ofseismo-sensory lines and departments of the brain.