Chaetostoma vasquezi, a new species of armoured catfish of Guayana Shield, Bolivar State, Venezuela (Siluroidei: Loricariidae): description and biogeographical considerations. Memoria de la Sociedad de Ciencias Naturales La Salle, 57(147), Enero-Junio 1998: 53-65. 55 [Zoological Record Volume 135]