796 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [781 



I 



varidbile while in A. gracile they are quite distinct in living specimens, I 



although it must be confessed they were found with extreme difficulty I 

 in the alcoholic specimens. 



ORYGMA.TOBOTHRIUM, Diesing. 



Body elongated, articulate depressed. Head separated from body by a neck, with I 

 four opposite cup-shaped bothria, attached by a contractile pedicel, highly versatile, I 

 and each provided with two scrobiculiform supplementary disks (auxiliary acctabula). I 

 Genital apertures marginal. (Diesing.) 



Van Beneden originally describetl the species 0. versatile Dies, under 

 the name Anthobothrium musteli. The species was taken out of the 

 genus Anthobothrium by Diesing on account of the two supplemental 

 disks on each of the bothria. 



The name Anthobothrium was retained by Diesing, and is used in this 

 paper, to designate those Tetrabothriidw whose bothria are unprovided 

 with auxiliary acetabuia. 



With regard to the supplemental disks at the center of the bothria 

 Van Beneden says : 



Upon studying theso appendages (bothria) with the aid of a compressor, other 

 characters appear which seem to be peculiar to this species. In the middle there is 

 a circular band surrounded with fascicles of muscular fibers making a circle at thfe 

 center which produces the effect of a cupping disk. 



The essential generic characters of these specimens, from Carcharias, 

 are about as follows : 



Body elongated, articulate, depressed. Head separated from body by 

 a neck, with four opposite cup-shaped bothria attached by short com 

 tractile pedicels, highly versatile, each provided with a single suppled 

 mental disk on anterior end of border. Border of bothria entire, with- 

 out loculi. Genital apertures marginal. 



In 0. crispum (Tetrabothrium (Anthobothrium) crispum Molin), the 

 second of the two species which Diesing includes in this genus, it ap- 

 pears to me, judging from Molin's figure, that the " central umbo" of 

 that author, while probably of the same nature as Yan Beneden's " cir- 

 cular baud," is not to be regarded as a supplemental disk. 



Whatever may be the final disposition of the genus Orygmatobothrium 

 there can be little doubt of the relationship of 0. angustum to Van 

 Beneden's Anthobothrium musteli.* 



* 



17. Orygmatobothrium angustum Lt. 



L Plate vii, Fig. 3.] 



Report of U. S. Fish Commissioner for 1836, pp. 4G8-9, Plate in, Figs. 1-3. 



In the summer of 1887 I obtained this parasite of the dusky shark 

 (Carcharias obscurus) on two different occasions. I give tbe following 



*Zschokke's admirable monograph, Eecherches sur Structure An at, et Tfist. des Ces- 

 todes (M6m. Inst. nat. Gendv., Vol. xvn, 188S), which reached me before these notes 

 were published, leaves no doubt whatever about the presence of two auxiliary accta- 

 bula on each bothrium of Anthobothrium (Orygmatobothrium) musteli Van Ben., and of 

 Orygmatobothrium longicalle Zschokke. 



