124 PROCEEDINGS OF THE NATIONAL MUSEUM vol. S8 



This species, which resembles H. afpendiculatus in many of its 

 characters, differs from that species markedly in the relative size of 

 the suckers. Whereas the diameter of the ventral sucker in H. 

 appendiculatus is about twice that of the oral sucker, in H. levinseni 

 the suckers are nearly equal, the oral sucker often being slightly 

 larger than the ventral. 



Hosts. — ^Lumpfish {Gycloptet^bs lumpus)^ common codfish {Gadus 

 morrhua), tilefish {Lopholatilus chamaeleonticeps) , whiting {Me7'- 

 luccius bilinearis), pollack {PoUachius virens), codling {Urophycis 

 chuss). 



Record of collections.— Ouq (U.S.N.M. No. 8330), collected July 

 10, 1926, from lumpfish. Measurements in balsam: Length, 1.26 

 mm., breadth, 0.53 mm.; diameter of oral sucker, 0.15 mm., of 

 pharynx, O.OT mm., of ventral sucker, 0.13 mm. ; ova, much crowded 

 and difficult to measure, about 0.018 by 0.012 mm. 



From common codfish: Fifty-three (U.S.N.M. No. 8331), col- 

 lected December 13, 1894, from one cod. Measurements in formalin : 

 Length, 2.73 mm.; breadth, 0.41 nmi. ; diameter of oral sucker, 0.22 

 mm., of pharynx, 0.11 mm., of ventral sucker, 0.22 mm.; ova, 0.025 

 by 0.014 mm. Average of six in balsam, lengths from 1.26 to 2.03 

 mm. : Length, 1.71 mm. ; breadth, 0.39 mm. ; diameter of oral sucker, 

 0.20 mm., of pharynx, 0.10 mm., of ventral sucker, 0.19 mm.; length 

 of appendage, 0.26 mm. ; ova, 0.024 by 0.012 mm. 



One, collected December 21, 1903; 30 fishes examined. Five, col- 

 lected July 15, 1926 ; 4 fishes examined. 



The eggs in most of these distomes from the cod are not collapsed 

 and appear to be distinctly larger than those in the distomes from 

 the pollack, etc. In one of the mounted specimens, however, some 

 of the eggs are collapsed and resemble those in distomes from other 

 hosts rather closely. 



From tilefish : Distomum ocreatum Molin, Bull. U. S. Fish Comm. 

 for 1899, p. 472, 1901. One of the larger specimens from this host 

 (U.S.N.M. No. 8332) has the following dimensions, in balsam: 

 Length, 2.38 mm., breadth, 0.42 mm.; diameter of oral sucker, 0.21 

 mm., pharynx, 0.10 mm., ventral sucker, 0.21 mm.; ova, 0.023 by 

 0.012. The seminal vesicle was not seen distinctly to be in two 

 sections, and the prostate begins a little in front of the ventral 

 sucker. 



From whiting: One, collected July 23, 1923. Measurements, bal- 

 sam: Length, 0.98 mm., breadth, 0.25 mm.; diameter of oral sucker, 

 0.12 mm., of pharynx, 0.06 mm., of ventral sucker, 0.10 mm.; ova 

 crowded and collapsed, about 0.018 by 0.009 mm. 



One (U.S.N.M. No. 8333), collected July 15, 1924. Measurements, 

 balsam: Length, 1.40 mm., (posterior end missing); breadth, 0.30 



