THE CH^TOGNATHA. 



59 



both rows comparatively short and triangular. Vestibular ridge with rounded 

 prominences fewer than the teeth, ridge about the same length as the posterior row. 



Posterior 



teeth. 



12 

 10-11 

 8-12 

 8-13 



9 

 7-10 

 5-6 

 6 

 2-6 

 5-6 

 3-4 



General Distribution. — The general table of Chaetognath occurrences and the liable 

 of average specimens following show that this form is essentially epiplanktouic. 

 Plentiful at all horizons to 100 fathoms, it yielded only a single damaged specimen 

 below that level in the closing-net (21 b, 200 to 100 fathoms). It occurred, naturally 

 enough, in the open serial nets lowered to greater depths, but may have entered these at 

 any point. The captures with open nets are analysed in the table following * : — 



At 



It is fairly obvious from the percentages of hauls in which the species occurred 

 that the expectation of meeting with serratodentata increases with the depth down to 



* This table is to be read as a sentence from lot't to right. 



t Throughout the discussion of distributions, the " average specimens "' are averaged over all hauls at the depth 

 mentioned ; not merely over those in wliicli the species occurred. See also note t on ne.xt page. 



