A revision of the literary data showed that the name Trichosoma carbonis Rudolphi, 1819 has to be considered a nomen nudum, which is invalid and unavailable according to the International Code of Zoological Nomenclature. The first recognisable description of the nematode designated Capillaria carbonis (Rudolphi) is that by Dubinin & Dubinina (1940) and, consequently, the correct valid name of this species is Baruscapillaria carbonis (Dubinin & Dubinina, 1940) n. comb. However, due to its inadequate description, it should be considered a species inquirenda. It is highly probable that the records of “Capillaria carbonis” by subsequent authors related, in fact, to more than one species. The nematodes recently collected from the small intestine of the common cormorant Phalacrocorax carbo (L.) from southern Moravia, Czech Republic, differ considerably from Baruscapillaria carbonis mainly in the structure of the male caudal end and are considered to represent a new species, B. rudolphii n. sp. This is characterised mainly by the length of spicule (1.25 mm), presence of a non-spiny spicular sheath, structure of the male caudal end, absence of a vulvar appendage in female and by various body and organ measurements. Since Trichosoma corvorum Rudolphi, 1819 is also a nomen nudum, the valid name of the intestinal capillariid which parasitises mainly birds of the genus Corvus in the Palaearctic region is Baruscapillaria resectum (Dujardin, 1845) n. comb. (syn. Trichosomum resectum Dujardin, 1845).