NOTES ON THE IDENTIFICATION OF CH/ETOGXATHA. 79 



10. Posterior teeth more than 8 in number II. 



11. Middle third of body of equal width Sagilta biptinctata. 



11. Body much wider at middle of length Sagitla eiijiata. 



12. Irregular transverse septa present on trunk Sagitla viinima. 



12. Irregular transverse septa absent on trunk 13. 



13. At least 50 per cent, of posterior fin in front of septum 14. 



13. Less than 50 per cent, of posterior fin in front of septum 18. 



14. Posterior fin widest in front of septum Sagilta zetesios . 



14. Posterior fin widest at or behind septum 15. 



15. Posterior fin shorter than anterior fin 16. 



15- Posterior fin as long or longer than anterior fin 17. 



16. Posterior teeth 9 to 15 in number Sagitla piihhra. 



16. Posterior teeth 15 to 23 in number Sagilta siboga. 



17. Anterior fin reaching to middle of ventral ganglion Sagilta planctonis. 



1 7 . Anterior fin not reaching to ventral ganglion Sagilta decipiens. 



18. Posterior fin shorter than anterior fin Sagilta ferox. 



18. Posterior fin as long or longer than anterior fin 19. 



19. Corona ciliata extends anteriorly beyond eyes Sagilta robusta. 



19. Corona ciliata not extending to eyes 20. 



20. Middle third of body of equal width Sagilta neglecta. 



20. Body of equal width from the ventral ganglion to the seminal vesicles. 



Sagilta regularis. 



If (19) the corona ciliata is absent the following criteria may 

 be used : 



19. Middle third of body equally wide Sagilta neglecta. 



19. Body equally wide from ventral ganglion to the seminal vesicles. .^a^/Z/s regularis. 



19. Body equally wide from just behind the neck to immediately in front of the tail 



septum Sagilta robusta. 



Key for Determination of the Species of Sagitta to be used for 



Poorly Preserved Material. 



I. Species with collarette 12 



1. Species without collarette 2 



2. Shaft of seizing jaws serrated Sagilta serralodentata 



2. Shaft of seizing jaws not serrated 3 



3. Irregular transverse septa present on trunk Sagitla fninirna 



3. Irregular transverse septa absent 4 



4. Length of anterior fin from 44 to 66 per cent, of the total length, anterior fin and 



posterior fins confluent Sagitta whartotti. 



4. Length of anterior fins never as much as 40 per cent, of total length, always an 



interval between anterior and posterior fin 5 



5. Tail 16 to 27 per cent, of the total length 6 



5. Tail 28 to 35 per cent, of total length 7 



6. Posterior teeth less than 8 in number 8 



6. Posterior teeth more than 8 in number 9 



7. Jaws more than 8 in number Sagitta viacrocephala 



7. Jaws less than 8 in number Sagitta bedoti 



8. Anterior teeth X to 4 in number Sagitla hexaplera. 



