HALLAZGO DE UNA ESPECIE NUEVA DEL GENERO PETALODISTOMUM Johnston, 1913 (TREMATODA: GORGODERIDAE) EN LOS TIBURONES DE LAS COSTAS DE MANZANILLO, COLIMA

Resumen

In the present paper the author describes a new species of Trematoda, Petalodistomum pacificum found in the celomic cavity of sharks from the Pacific Ocean. This species differs from P. polycladium Johnston, 1913 and from P. yorkei (Nagaty, 1930), in the form and situation of the vitellaria, the number and grouping of the testicular folicules, the development of the uterus, the structure of the main stem of the excretory system and the shape of the intestinal caeca. 
The author, considering the variation of the structures as found in the study of numerous specimens, reduces the genus Nagmia (Nagaty, 1930) to a synonym of Petalodistomum, with three species P. polycladium, P. yorkei and P. pacificum n. sp.
A new diagnosis of the genus has also been made by the author.