On Oswaldella billardi Briggs, 1938 and O. erratum spec, nov., two antarctic hydroid species (Cnidaria, Hydrozoa)

The type material of Oswaldella billardi Briggs, 1938, has been re-examined and a complete description and figures are presented. The study of that material has allowed to reconsider the systematic position of all the material previously assigned to O. billardi and to determine that part of it belongs to another species. Since it is clearly different from the remaining species of the genus, it is described as Oswaldella erratum spec. nov. Resumen: Se ha revisado y redescrito el material tipo de Oswaldella billardi Briggs, 1938. Su estudio ha permitido reconsiderar la posición sistemática de todo el material anteriormente asignado a O. billardi y, así, determinar que parte del mismo pertenece a otra especie. Ya que dicha especie es claramente diferente de las otras especies del género, se describe como Oswaldella erratum spec. nov.