17^ Papers from the Marine Biological Laboratory at Tortugas. 



breadth 0.4; proboscis, length, estimated, 3, diameter, exclusive of hooks, 

 0.19; length of longest hook 0.20. In an alcoholic specimen, somewhat 

 more slender than usual, the average length of the last four segments was 

 3.5, the breadth, 0.09. 



From the nurse-shark (Ginglimostoma cirratum} : 



July 2, one scolex and strobile, and a fragment, spiral valve. 



July 6, 59, in upper part of spiral valve. 



19. Rhynchobothrium tenuispine Linton. 



Report U. S. F. C, 1887, pp. 837-838, plate xn, figs, i, 2. Proc. U. S. Nat. 

 Mus., vol. xx, pp. 448-449, plate xxxiv, fig. 8. Bull. U. S. F. C, 1899, 

 pp. 426, 433. Bull. Bureau of Fisheries, vol. xxiv, p. 348. 



Numerous small tetrarhynchs from the nurse-shark (Ginglimostoma 

 cirratwn} agree very closely with this species, and are for the present re- 

 ferred to it. 



The neck is rather long and slender, often long-pyriform, tapering for- 

 ward, with red pigment at the base in front of and beside the contractile 

 bulbs. The neck in many cases was strongly spinose, the spines on the neck 

 being considerably larger than those on the proboscis. These neck -spines 

 are much less dense on some than on others, and are therefore evidently 

 an evanescent character. The proboscides are relatively very long, with 

 bulbous base, and are armed with minute hooks. The hooks on the base of 

 the proboscides agree closely with this species, while those towards the distal 

 end are, perhaps, a little smaller and more slender. The first segments are 

 in some cases moniliform. 



Measurements were made of specimens mounted in balsam and showed 

 a close correspondence with the dimensions given for this species. A few 

 of these measurements, in millimeters, are here given : Length of head and 

 neck i.io; breadth of head 0.28, of neck, behind head, 0.16, at contractile 

 bulbs 0.22 ; length of contractile bulbs 0.40 ; length of first segment 0.09, 

 breadth 0.12; diameter of proboscis at tumid base 0.025, m front of tumid 

 base 0.018. The length in life is about 5 mm. 



Seventy-five specimens were collected from the spiral valve of a nurse- 

 shark on July 5, and numerous specimens were obtained on July 6. In both 

 cases the shark was large. 



20. Rhynchobothrium lineatum sp. nov. 



(Plate 6, figs. 39-43-) 



Bothria elliptical, entire, widely flaring at base; neck cylindrical, with 

 evanescent spines ; contractile bulbs long and slender ; sheaths in close 

 spirals ; proboscides very long, slender, and slightly enlarged near the base, 

 hooks very minute and closely set. Body continuous without any constric- 

 tion behind the bulbs, linear, increasing in breadth very little posteriorly and 



