18 



T. AIDA. 



the tactile prominences of the first kind are shown with clear circles and 

 those of the second with black spots. It may be gathered from the 

 figures that the number of tactile prominences of the first kind in each 

 transverse row, is reduced from (> in the anterior part of the trunk to 4 in 

 the posterior half, beginning from the level of the first lateral fin. In 

 each transverse row of the prominences of the second kind 4 lie exactly 

 between the prominences of the first kind. It must be noted, however, 

 that the alternation of the rows of prominences of the two kinds 

 are not rigidly carried out, as sometimes two transverse rows of the 

 second kind are placed between the rows of prominences of the first 

 kind. Tins irregularity commonly occurs in the other species having 

 a similar arrangement of tactile prominences. 



In the caudal segment, the tactile prominences are comparatively 

 few ; and in the head they are found only on the dorsal surface. 



Sagitta bipunctata (small specimens), Sagitta neglecta, Sagitta 

 minima, Sagitta serratodentata, Krohnia viridis, Krohnia foliacea, and 

 Spadella draco have all a more or less similar arrangement of tactile 

 prominences, but none of them shows such a regularity as is found in 

 this species. 



9. Sagitta hispida, Conant. 

 (Fig 9.) 

 Literature : Conant (5). 



Whole length of the body 11mm. that of the caudal segment 

 2.8mm., and the breadth 0.7mm. 



The epidermis thickens at the neck as in Sagitta bipunctata. The 

 muscular coat is thick and gives the animal a stout appearance. The 

 two pairs of lateral fins are separated ; the first fin is shorter and begins 

 slightly behind the abdominal ganglion (in the young, smaller individu- 

 als, it begins at the middle of the abdominal ganglion) ; the second fin is 

 longer, extending to the spermatic vesicle. The head is comparatively 

 large, and has 7-8 seizing hooks, 11-17 posterior teeth, and 7-8 ante- 

 rior teeth. Our specimens have a greater number of seizing hooks and 



