1911] Micliael: CJiaetogiiatJia of tJic San Diego Region. 27 



12. Body transparent. First third of anterior fin without the usual 

 rays Sagitta pulchra. 



12. Body opaque. Anterior fin with rays throughout.-Sagitta sibogae. 



13. Tail 28 to 40 per cent of total length. No constriction at tail- 



septum Sagitta decipiens. 



13. Tail not over 25 per cent of total length. Constriction at tail- 



septum evident Sagitta bipunctata. 



14. Collarette extends to anterior fins 1.5 



14. Collarette never extends much over half way to anterior fins 16 



1.5. Anterior fin longer than posterior fin Sagitta ferox. 



15. Anterior fin shorter than posterior fin Sagitta regularis. 



16. Anterior fin extends to ventral ganglion 17 



16. Anterior fin never extends to ventral ganglion Sagitta hispida. 



17. Collarette exceedingly small. Sexually mature at a length from 



5 to 6 mm Sagitta tenuis. 



17. Collarette well developed, extending nearly half way to ventral 



ganglion. Never sexually mature under 10 mm 



Sagitta neglecta. 



KEY TO THE SPECIES OE EUKROHNIA 

 1. Lateral fin extends from the region of the ventral ganglion to 

 somewhat behind the tail-septum; never reaches to seminal 



vesicles; more than 60 per cent in front of the tail-septum 



Eukrohnia hamata. 



1. Cephalic limit of lateral fin never more than half the distance 



from the tail-septum to the ventral ganglion; extends caud- 

 ally to the seminal vesicles; more than 40 per cent of fin be- 

 hind septum 2 



2. Body width about 4 per cent of total length. Tail 30 to 40 per 



cent of total length. Seizing jaws evenly curved, 6 to 9 in 



number. Teeth 9 to 13 Eukrohnia subtilis. 



2. Body width about 5 per cent of total length. Tail 25 to 41 per 

 cent of total length (usually not over 33 per cent). Teeth 

 11 to 15. Seizing jaws 6 to 9, with the convex edge made up 

 of two curves, the junction of which makes an obtuse angle at 

 a point about one-fourth the length of the jaw proximad of 

 the tip Eukrohnia pacifica. 



KEY TO THE SPECIES OF SPADELLA. 



1. Average width of collarette nearly half that of body, widest 

 slightly anterior to the tail-septum. Length of fin always less 

 than 5 times its width. Anterior teeth 7 to 10. Posterior 

 teeth 11 to 16 Spadella draco. 



1. Average width of collarette much less than half that of body; 

 widest slightly posterior to head. Length of fin always more 

 than 5 times its width. Anterior teeth 3 to 5. Posterior 

 teeth 3 to 4 '. Spadella cephaloptera. 



