The position of the nasal sacs and nostrils, as well as some features of the brain structure in antiarchs (placoderm fishes) are analyzed, based mainly on the examples of Bothriolepis and Asterolepis. A new possible reconstruction of the olfactory system and brain in antiarchs is proposed. The paired nasal sacs are closely located to the anterior wall of the telencephalon; tracti olfactorii are absent; telencephalon is situated anterior to the diencephalon, as it was reconstructed for other placoderms; and the epiphysis process is elongated. The mesencephalon, cerebellum and medula oblongata, bearing the fossa romboidea, are placed posterior to the diencephalon in the otico-occipital part of the endocranium.

New data on the placoderm fish Plourdosteus livonicus (Eastman, 1896) from the Lower Frasnian deposits of the Mikhaylovsky Mine in the Kursk Region is described. These remains are currently housed at the Earth Science Museum of Lomonosov Moscow State University. The medio-dorsal plate from this locality allows reconstructing its form and proportion, as also early unknown anterior division of the bone. Only small fragments of medio-dorsal plates were formerly described and figured for P. livonicus from this and other localities in European Russia. So, the new data from the Mikhaylovsky Mine adds to the morphology information of this species. The medio-dorsals are of diagnostic significance and distinguish in the plourdosteids. The specimen from the Earth Science Museum’s collection is compared with the medio-dorsal plates of other Frasnian Plourdosteus species from the East-European platform.

The palaeoichthyological collection from the Bilovo locality in the Tver’ region (Famennian of the Main Devonian field), currently housed at the Andreapol Museum of Local History, is continued to be studied. Placoderm fishes of the family Bothriolepididae Cope predominate in the ichthyocomplex of this locality. Rare plates of large-bodied Bothriolepis sp. with a flattened armor were found at the Bilovo locality in clay deposits in addition to numerous remains of crested bothriolepidids. The material on Bothriolepis sp. is represented by three posterior medio-dorsal plates only. These plates are described, figured and compared with a similar material on Late Devonian bothriolepidids from the Main Devonian field and other regions. A brief characteristic of the Bilovo locality is given as well.