Helminth Fauna of the Dry Tortugas. 169 



be segmenting. A few of the early segmentation stages are shown in fig. 8. 

 A few measurements, in millimeters, were made on the living worm with 

 the following results: Length 178; diameter of head 4.5; greatest breadth 

 of body 5, about the middle; last segment, length 2.5, breadth 2.25, with 

 ripe ova, which were 0.035 an d 0.032 in the two principal diameters. 



8. Anthocephalum gracile Linton. 



Report U. S. F. C. 1887. pp. 794-796, plate vn, figs. 1-2. Bull. U. S. F. C, 1899, 

 pp. 275-411. Bull. Bureau of Fisheries, vol. xxiv, p. 347. 



Twelve specimens were found in the spiral valve of the sting-ray (Dasy- 

 atis say}, July 10. 



The following measurements, in millimeters, were taken from a speci- 

 men mounted in balsam: Length 6; diameter of head 0.040; breadth of 

 body just behind head o.n ; last segment, length 1.49, breadth o.n. Stro- 

 bile linear. 



9. Undetermined Cestode. 

 (Plate i, figs. 5, 6, 7.) 



One immature strobile from the spiral valve of the cub-shark (Carcha- 

 rhiints platydon}, July 12, probably belongs to a new genus. It was nearly 

 dark when this specimen was collected, and it was not in good enough con- 

 dition to risk keeping it in sea-water over night. The appearance of the 

 living worm was that of having a lappet at the posterior end of each both- 

 rium. In the preserved and mounted specimen this proves to be a loculus 

 produced by a transverse costa near the posterior end of the bothrium. Each 

 bothrium is also provided with a single auxiliary acetabulum at the anterior 

 end. There are no hooks on the bothria. So far as I know, there is no 

 genus of cestodes in which the bothria are without hooks and at th3 same 

 time possess auxiliary acetabula and costa. 



The strobile is filiform, with ten segments, all of which are singularly 

 long and slender. The neck is also long and slender, and both neck and 

 segments are finely serrate. The reproductive apertures are marginal and 

 are situated at about the posterior third. The last segment is attenuate at 

 the posterior end. 



Dimensions, in millimeters, of the living worm: Length 15; breadth 

 of head (variable) 0.4; bothrium (variable), length 0.29, breadth 0.19; 

 distance to first segment 5.8; first segment, length 0.35, breadth 0.12; last 

 segment, length 1.40, breadth 0.15. In balsam the diameter of the head 

 is 0.40, while that of the neck near the head is 0.08. 



PEDIBOTHRIUM 1 gen. nov. 



Body tenuiform, articulate, head separated from the body by a distinct 

 neck, and provided with four distinct, cruciform, armed bothria, without 

 auxiliary suckers, costae or loculi. 



n-e'Stos = even, i. e., without costa. 



