1911] Michael: CJtaetognatJia of tJie San Diego Region. 49 



laris nearly half as long as posterior fin, while the fin in S. 

 neglecta is very little shorter than posterior fin. The posterior 

 fin in the latter species extends further in front of tail-septum 

 than in S. regularis. Measurements taken from Aida's (1897) 

 drawings of the two species show the following relations. 



TABLE 11 

 Measurements taken from Aida 's Drawingsi 



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



2 Per cent of posterior fin in front of tail-sej^tum. 



In the matter of relative lengths of anterior and posterior 

 fins of the two species the drawings do not show much differ- 

 ence. The relative per cent of posterior fin in front of tail- 

 septum has more significance, although a large number of 

 measurements of both species are necessary in order to definitely 

 establish any specific difference in this regard. 



Fowler (1906) has defined certain other characteristics, 

 some of which seem invalid. He claims (1906, p. 16) that in 

 S. neglecta "the tail is slightly shorter" than in S. regularis, 

 which he regards as one of the "main points of difference." 

 [Italics mine.] However, when his data are brought together 

 as in the accompanying table, it is seen that for the lengths of 



