Silver-impregnated miracidia of Gorgoderina attenuata, Phyllodistomum superbum, P. staffordi, and P. undulans all have 15 epidermal cells in 3 tiers, expressed by the formula 6-6-3. Two variations in P. undulans are 5-6-3 and 6-5-3; also 1 specimen of P. superbum contains 5 cells at the anterior end and 8 additional ones not arranged in recognizable tiers. Three kinds of pores are present: 4 groups of 3 or more pores on the terebratorium; 2 excretory pores, usually located between the second and third tiers; and 2 small pores at the posterior tip, evidently associated with a pair of bristles. End view examination shows that all 3 kinds of pores are in bilateral symmetry; allowing for slight torsion on fixation, and considering the 2 excretory pores to be ventro-lateral, the terebratorium bears a ventro-lateral and a dorso-lateral group of pores on each side, and the 2 smaller posterior pores are laterally placed. Among the gorgoderid species incldued in this study, no consistent differences have been observed either in the epidermal cell pattern or in the number and location of pores.