SYSTEMATIC NOTES 387 



an embryo is about 45 x 36/* in diameter, while the embryo is about 24 x 45^. The lateral pairs of 

 hooks are 12 it in length and the central pair 18//,. The proportions of these hooks is not represented 

 accurately in Fig. 20. 



The ventral and dorsal trunks of the excretory system differ in diameter and have rather thin walls. 

 The differences between this new form and Tetrabothrius affinis lie in the shape of the body and in the 

 arrangement of the longitudinal muscles. These characters also differ from those found in other species 

 of Tetrabothrius. Further differences in structure and in the eggs and the embryos have been given in 

 Table 1. 



' ' '.**>*< ft H -ft ?«f * 3 ,-w. 



- v ^vS^it'L , yi:iU ; 4f-'i , ''(au ; '' 



Figs. 1 6-20. Tetrabothrius schaeferi sp.n. from Blue Whale. 16, Cross-section of semi-gravid segment with eggs; 17, cross- 

 section through longitudinal muscle; 18, cross-section of segment showing cirrus-sac and vagina; 19, cross-section showing 

 cirrus-sac and everted cirrus; 20, egg. 



Table 1 . Measurements of Tetrabothriids occurring in the Cetacea from the Discovery Collections 



