Helminth Fauna of the Dry Tortugas. 179 



that very gradually. First distinct segments begin a short distance back 

 of neck, at first much broader than long, soon becoming squarish, then 

 longer than broad, all with crenulate margins. Genital aperture marginal 

 in a deep rounded notch at about the posterior third; ripe segments with 

 ova not seen ; longest segment two and one-half times as long as broad. 



There are many points of resemblance between this species and R. 

 longicorne. Length of living specimens as much as 30 mm. ; of alcoholic 

 specimens 1 8 to 20 mm. 



Dimensions, in balsam, given in millimeters : Length 20 ; length of head 

 and neck 3.28; bothrium, length 0.27, breadth 0.27; diameter of neck, ante- 

 rior 0.23, posterior 0.40; bulbs, length 1.36, breadth 0.14; first distinct seg- 

 ment, length about 0.08, breadth 0.40; last segment, length 1.12, breadth 

 0.56; proboscis, length (estimated) 2.5; diameter at base 0.05, near distal 

 end 0.03; length of longest hooks 0.017. 



The segments, in this specimen, are twenty in number, and are somewhat 

 irregular in length, the last one not being the longest. The longest segment 

 measures 1.6 in length, and 0.67 in breadth. 



From the nurse-shark (Gingliniostoina cirratuin). 



July 6, four. July 15, seven and fragments. 



21. Rhynchobothrium curtum sp. nov. 



(Plate 6, figs. 44-47-) 



Bothria broad-elliptical or oval-elliptical and somewhat thick, placed on 

 the sides of the head which correspond to the lateral margins of the strobile. 

 Head, in side view, heart-shaped ; neck very short, shorter than bothria ; 

 bulbs oval-elliptical, sheaths nearly straight; proboscides short, hooks small. 

 Body at first a little narrower than neck ; first segments begin near neck, at 

 first much broader than long, but soon becoming as long as broad, then very 

 soon becoming longer than broad, with rounded corners and more or less 

 crenulated or indented margins ; marginal vessels conspicuous ; reproductive 

 aperture at about the posterior fourth. 



Only preserved specimens were seen; the largest specimen noted meas- 

 ured 10 mm. in length. 



Measurements, in millimeters, of a specimen mounted in balsam: Length 

 6; head, length 0.21, breadth 0.22; neck, length 0.06, breadth 0.07; breadth 

 of body behind neck o.io; distance to first distinct segment 0.08; first seg- 

 ment, length 0.02, breadth o.n. 



The hooks were not seen very distinctly, as no proboscis was everted. 

 A number of measurements showed that the longer hooks were about 0.024 

 in length. Only one was found which measured as much as 0.04. It was 

 near the base of the proboscis. 



As the increase in length and breadth of segments is much the same in 

 different specimens, the following measurements of all the segments in one 

 example are given : 



