170 Papers from the Marine Biological Laboratory at Tortugas. 



Each bothrium is strengthened by a strong muscular ring, with a thin, 

 more or less leaf-like border, and is armed at the anterior end with a pair 

 of compound hooks. Each hook consists of two unequal prongs, which rise 

 from a flattened base. This basal part of the hook has a characteristic shape 

 in each species. The neck is traversed by conspicuous bundles of longi- 

 tudinal muscle fibers. 



This genus is separated from the genus Acanthobothrium by the absence 

 of costa 3 , and from Phoreiobothrium by the character of the hooks, which 

 have two instead of three prongs, and further by the absence of loculi on 

 the bothria. 



The species P. globicephalum suggests in its general habit of body the 

 genus Onchobotlirinin, but there are no cost?e on the bothria, as in that genus. 



It is worthy of note that the hooks of P. globicephalum closely resemble 

 those figured by some authors, e. g., Zschokke, for Onchobothrium un- 

 cinatum. 



Diesing's genus Cylindrophorus, based on Wagener's Tetrabothrium sp., 

 is suggested as being possibly near this, but the character of a tubular 

 bothrium, as that must be understood from Wagener's figures, indicates an 

 essentially different structure from that shown by this genus. 



In like manner Diesing's genus Prosthecobothrium (Bothriiun corniitns 

 Duj., Oncli. coronatus Duj., Acanthobothrium, Dujardin, van Bcneden. 

 etc.), while resembling it in the absence of costas and in the presence of 

 forked hooks on each bothrium, differs in having a foliaceous appendage 

 on the posterior end of each bothrium. 



10. Pedibothrium globicephalum gen. et sp. nov. 



(Plate 2, figs. 9-16.) 



Head, especially in preserved specimens, globular. Bothria ovate, pro- 

 jecting in front of hooks, and supplied with prominent marginal border; 

 each armed with a pair of small two-pronged hooks. The prongs are only 

 moderately curved and are of unequal size, the inner one being the shorter. 

 The common base is somewhat elongated. The neck is distinct, but the 

 first segments begin as faint transverse lines at a distance from the head 

 equal to three or more times its length. Strong muscular bundles lie in the 

 neck near the head. 



The first segments are broader than long, then squarish, then longer 

 than broad, with rounded angles. Ripe segments much longer than broad, 

 in some cases slightly narrowed at the extremities, especially the anterior. 

 Genital cloaca on lateral margin, a little behind the middle, vagina in front 

 of the cirrus, at first at right angles to the axis of the segment, then parallel 

 with it to the paired ovaries near the posterior end of the segment. 



The vitelline glands form a marginal border throughout, except at the 

 extremities. As a rule they extend but a short way back of the ovaries. 



