[103] NOTES ON ENTOZOA OF MAIilNE FISHES. 821 



four, subtriangular iu closely appresscd marginal pairs. When seen 

 from the lateral side the two bothria, which are then in view, resemble 

 right triangles with their acute angles truncated, and so placed with 

 reference to each other that the hypothenuses are parallel and separated 

 by a narrow space along the median line of the head. The shorter legs 

 of the triangles then form the antero-lateral boundary of the head and 

 the longer legs, the postero-lateral boundary. The truncated acute an- 

 gles form the apex and base of the head, respectively. There appears to 

 be a faint supplemental disk near the anterior end of each bothrium in 

 front of the hooks, although its identification in the alcoholic specimen 

 is not altogether satisfactory. At the posterior end of each bothrium 

 there is a highly characteristic modification, the exact nature of which 

 I am not sure that I understand. In the sketches made of the living 

 worm it appears to be a transverse costa, which is convex toward the 

 front, lying near the posterior end of the bothrium and making a locu- 

 lus in the face of the bothrium. In the alcoholic specimen, however, 

 the appearance is somewhat different. Each bothrium appears to be- 

 come somewhat tubular at its posterior extremity, and what, in the liv- 

 ing specimen, appeared to be a posterior loculus, now seems to be the 

 thickened tubular end of the bothrium. The inner boundary of this 

 tubular end extends farther back than the outer boundary, so that the 

 appearance iu a specimen which had been slightly compressed would, 

 of course, be the same as if the bothrium were crossed by a transverse 

 costa near the posterior end. The faces of the bothrium are but little 

 hollowed out. 



Each bothrium bears near its anterior border a very characteristic 

 set of compound hooks. The hooks showed with perfect distinctness 

 through the transparent tissues of the head. The system of hooks on 

 each bothrium is in three distinct parts, all of which are joined together. 

 The arrangement of the hooks is shown in the sketches of the head. 

 It is, in brief, as follows: Two booklets, or rather the two prongs of 

 a single hook, terminate the system on the inner side of the bothrium. 

 These inner prongs are long and slender, directed backward, and lie 

 close beside the corresponding pair in the other lateral bothrium. These 

 prongs are terminal forks of a slender, arcuate bar, which is convex 

 iu front and articulates by means of an overlapping joint with a short, 

 slender process, which, in turn, articulates by a plain hinge-joint with 

 the basal prolongations of the outer set of booklets at the marginal 

 angle of the bothrium. This latter cluster appears at first sight to 

 consist of three booklets. There are iu reality but two. These, like 

 the inner booklets, are forks of a basal part. They are long and slender, 

 recurved, and a little larger than the inner pair. The basal part of the 

 outer booklets sends back a subcutaneous prolongation, which, on ac- 

 count of the transparency of the soft tissues of the head, looks as if 

 it were a third prong of the compound hook. It can be easily proved 

 to lie beneath the external coat of soft tissue. The booklets are hoi- 



