THE TREMATODA 



(Fig. II. 6) ; Onchocotijle, Dies., on gills of Elasmobranchs. B. Suckers 

 in a transverse row posteriorly. Hexacotyle, Blv. (Fig. II. 2); H. 

 thynni, de la Koche. Plectanocotyle, Dies., has only six suckers. SUB- 

 FAMILY 2. POLYSTOMINAE, with six posterior suckers ; without anterior 

 buccal suckers. Polystomum, Zeder ; P. integerrimum, Frol., bladder of 

 Frog and Toad (Fig. V. 1, 2 ; and for an account see 49). P. ocel- 

 latum, End., pharynx of Emys europaea. Erpocotyle, v. Ben. and Hesse ; 

 Diplobothrium, Leuckt. ; Sphyranura, Wright ; S. osleri, Wr., on skin of 

 Necturus lateralis (see 48). FAMILY 4. MICROCOTYLIDAE, with two "buccal" 

 suckers and numerous small posterior suckers carried on a variously 



FIG. II. 



shaped marginal cotylophore ; genital pore median ; vagina may open 

 on the left side (see 37). Microcotyle, v. Ben. and H. (Fig. III. 1) ; 

 Gastrocotyle, v. Ben. and H. ; G. trachuri, v. Ben. and H., on the gills of 

 Caranx trachurus. Axine, Abildgaard ; A. belones, Abild. ; A. triglae, 

 v. B. and H. FAMILY 5. GYRODACTYLiDAE. 1 Elongated body with one or 

 two pairs of retractile cephalic lobes, carrying the openings of glands ; 

 anterior suckers may also be present ; the caudal disc does not carry 

 suckers, but is armed with peculiar hooks, central and marginal ; 

 eyes are usually present anteriorly ; genital pore median ; no vagina. 



1 Dionchus, Goto (Joiirn. Sci. Coll. Imp. Univ., Tokyo, xii. 1899, p. 286), 

 combines several characters of this and the preceding family. 



