1911J Michael: Chaetogiiafha of the Sa)i Diego Region. 45 



over the posterior half of the ridge. Wing of ridge covers all but the 

 first tooth. In some rare instances two teeth are left exposed, and in 

 others all the teeth are covered. External process short and thick, 

 about one-third the length of ridge, and from two to three times longer 

 than broad. Notch extends inward beyond the fourth and nearly to 

 the fifth tooth. 



Anterior teeth 4 to 7 in number. Closely set and increasing in size as 

 they approach internal angle. They are narrow in proportion to their 

 height. Posterior teeth 11 to 15 in number. Similar in form to anterior 

 teeth but higher and relatively narrower. 



Seising jmvs (pi. 4, fig. 33) 8 to 9, rarely lU in number. Curvature 

 about 12.7 per cent. Points with oval base. Tip of point rather blunt. 

 Curvature of back greater than curvature of edge of point so that apex 

 lies nearer edge. Point imbedded from 20 to 25 per cent of its height 

 into shaft. Base of point and top of shaft converge in approaching back 

 of jaw. Pulp-canal approximately central with the pulp evenly 

 distributed. 



TABLE 9 



Measurements of Sagittu plankton is^ 



1 All measurements made in per cent of total length of animal. 



2 Per cent of posterior fin in front of tail-septum. 



In my material none of the individuals was sexually mature. The 

 ovaries were slender and the eggs small, notwithstanding the fact that 

 the ovaries extended to the cephalic end of anterior fin. Most of the 

 specimens show apparent transverse septa across the intestine, as 

 described by Doncaster (1902a) for S. minima, and his exijlanation of 

 this fact as due to the drawing apart of the walls of the intestine is 

 evidently true in S. planktonis. One specimen still retained the corona 

 ciliata (pi. 7, §g. 46). It is skein-shaped with more than three-fourths 

 on head, and extending from one-third to one-half'- its length anterior 

 to the eyes. 



