48 University of California Fuhlications in Zoology. [Vol. 8 



TABLE 10 

 Measurements of Sagitta neglecta^ 



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

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



In comparison with Fowler (1906) a number of differences 

 in some of the measurements are evident. He finds the tail to 

 vary from 26 to 37 per cent in individuals ranging from 7.5 to 

 10 mm. in length. In the San Diego specimens the variation 

 is only 26 to 30 per cent. The seizing jaws we found to vary 

 from 7 to 9, instead of from 5 to 8 in number as recorded in 

 the "Siboga" material. Fowler (1906) records the anterior 

 teeth as 3 to 7, the usual number, perhaps, being 6, w^hile San 

 Diego specimens present 5 as the greatest number. Similarly 

 S. neglccia from this region are provided with fewer posterior 

 teeth, 8 to 11 as against 9 to 15 recorded by Fowler (1906). 



From Aida (1897), however, we find the variation as fol- 

 lows : seizing jaws 8, anterior teeth 4 to 5, posterior teeth 10 to 

 12. Aida (1897) describes the tail as 24.3 per cent, but draws 

 it 35 per cent, and one is at a loss to know which expresses the 

 truth. Nevertheless there is striking agreement between Aida's 

 description and specimens from San Diego. 



I know of no two species more perplexing to identify than 

 ^Sf. )icglecta and 8. regularis, both first described by Aida (1897). 

 He defines the following differences. Anterior fin in S. regu- 



