Redescription of the Species of Gyrocotyle from the Ratfish, Hydrolagus colliei (Lay and Bennet), with Notes on the Morphology and Taxonomy of the Genus
Gyrocotyle fimbriata* Watson, 1911 and G. urna* (Grube and Wagener, 1852) from the spiral valve of Hydrolagus colliei of the Pacific Coast of N. America are redescribed. Two vars. of G. urna, f. magni-sponosa and f. parvispinosa, differing in size of the acetabular spines*, are distinguished. Chimaera monstrosa of the N. Atlantic and Mediterranean harbors 2 spp. of Gyrocotyle, apparently identical with the 2 spp. from H. colliei, both of which have hitherto been referred to the species G. urna. G. nigrosetosa Haswell, 1902, is considered a synonym of G. nrna (Grube and Wagener, 1852). The incomplete descriptions of the genotype, G. rugosa Diesing, 1850 (G. plana Linton, 1924) are discussed and a tentative specific diagnosis is presented. G. maxima MacDonagh, 1927, and Gyrocotyl-oides nybelini Fuhrmann, 1930, are allocated to species inquirendae because of inadequate descriptions. The reproductive system* and the posterior nerve ganglia and commissures* of Gyrocotyle are described in detail, with corrections of several errors and omissions in previously published descriptions. The free-swimming decacanth larva* and early postlarval stages* are described. Allocation of the genus Gyrocotyle to the Cestoda must be deemed provisional, since the life history (insofar as known), and much of the morphology of the worm, are atypical of the Class.