182 Papers from the Marine Biological Laboratory at Tortugas. 



base; among the latter are two which are larger than the others and stand 

 side by side. These two spines are quite conspicuous. They are of nearly 

 uniform size from the base to near the tip, where they terminate in a short 

 recurved, almost acuminate hook. These characters are best seen in the 

 figures. A third spine of the same general shape, but much smaller, stands 

 near the large pair. 



The segments begin immediately behind the neck, are few, four or five 

 in the example studied, increase in length rapidly, but remain rather narrow. 

 The last segment may be as long as the rest of the strobile ; reproductive 

 aperture marginal, a little back of the middle, making a shallow notch with 

 gently sloping sides. 



Dimensions, in millimeters, of a living specimen, a strobile with four 

 segments: Length 7.31 ; length of head and neck 1.68; length of bothrium 

 0.28 ; breadth of head 0.56, of neck 0.39 ; length of bulbs 0.84 ; distance from 

 base of neck to first distinct segment 0.07; length of first segment 0.14, of 

 second 0.42, of third 1.40, of fourth 3.60; breadth of third 0.19, of fourth 

 0.42 ; diameter of proboscis, exclusive of hooks, 0.04 ; length of longest hook 

 noted 0.023. In a specimen, mounted in balsam, there were five segments, 

 which had the following lengths: 0.08, 0.13, 0.45, 1.23, 3.48; length of head 

 and neck 1.25. 



Dimensions of a specimen in balsam: Length 5.97; length of bothrium 

 0.16; of head and neck 1.44; of bulbs 0.84; length of last segment 2.41. In 

 a specimen, which measured 6.62 in length, the fifth and last segment was 

 3.48 in length. The largest hook measured was 0.035 m length. 



From a sting-ray (Dasyatis say), July 10, ten, in spiral valve. 



24. Rhynchobothrium sp. 



(Plate 9, figs. 65-69.) 



This is probably a new species, but since only one specimen was found, 

 and it a scolex with the rudiment only of a strobile, it does not seem advisa- 

 ble to bestow a specific name upon it at present. The specimen was flat- 

 tened at the time of collecting- and is now mounted in balsam. The head 

 can be seen only in side view. The bothria approach each other anteriorly 

 and are widely flaring posteriorly. Their shape can not be made out exactly. 

 but they evidently have flexible borders and are probably about as broad 

 as they are long. The neck is also flattened and expands a short distance 

 behind the head until it is as wide or wider than the head. The bulbs are 

 long-fusiform, and the retractor muscles take their origin from the posterior 

 ends. The sheaths are coiled in loose spirals. The proboscides are rela- 

 tively very long and are armed with hooks which are short and of nearly 

 uniform size and shape. The strobile is rudimentary, shorter than the head 

 ;md neck and tapers to a blunt point at the posterior end. The lateral ves- 

 sels there meet and open by a terminal pore. Segments have begun to form, 

 but thcv are all vcrv short. 



