ECTOPAKASITIC TKEMATODES. 281 



a short distance before opening into the paired yolk-ducts. Testes 

 only about a dozen, small. 



Habitat. — Gills of scup {Stenotomus chrysops). 



Loc. — Newport, R. I. 



3Iicrocotyle hiatulœ n. sp. 

 (PI. XXI, fig. 29.) 



Body symmetrical, anteriorly blunt, 3.5 mm. long, of which 

 the posterior one-fourth bears about 23 pairs of suckers on either 

 side ; the sucker-bearing portion projecting slightly in front on 

 the ventral side. Oesophagus of moderate length ; the main in- 

 testinal branches of unecjual lengths, one of them extending much 

 more backwards into the sucker-bearing portion of the body, 

 with numerous bifurcating branches on the inner and outer 

 sides, those of the former being, however, very short. Common 

 genital pore a short distance in front of the hind end of the 

 oesophagus ; genital atrium with numerous conical, slightly re- 

 curved spines, ranging in length between 15 // and 18 n. Ovary 

 somewhat like a hastily written capital E of the current hand, 

 presenting a very convex border in front. The oviduct arises 

 on the right side, and undergoes one or tAvo windings on its course 

 obliquely backwards and towards the left side to the posterior 

 end of the ovary, where it turns forwards to become the ootyp. 

 Vitellaria extending fi-om near the hind end of the oesophagus 

 to the hind end of the body proper. Paired yolk-ducts arising 

 about one- fourth as much in front of the ovary as the common 

 genital opening, and uniting in the median line a short distance 

 in front of the ootyp ; the median yolk-duct opening into the 

 oviduct at a short distance from the ootyp. Vaginal opening 

 median and dorsal, as much beliind the front end of the intes- 



