Neotropical Monogenoidea. 36. Dactylogyrids from the gills of Rhamdia guatemalensis (Siluriformes: Pimelodidae) from cenotes of the Yucatan Peninsula, with proposal of Ameloblastella gen. n. and Aphanoblastella gen. n. (Dactylogyridae: Ancyrocephalinae). Comparative Parasitology, 67(1), January 2000: 76-84. 77 [Zoological Record Volume 136]