CHAETOGNATHA COLLECTED BY STEAMER ALBATROSS. 263 



SAGITTA PLANKTONIS Steinhaus. 



Sagitta planktonis Steinhaus (1896), p. 39.— Ritter-Zahony (1911), p. 29.— 



Michael, (1911), p. 44. 

 Sagitta zetesios Fowler (1905), p. 67; (1906), p. 22. 



Eighty-seven specimens were obtained, but unfortunately all except 

 one were preserved in alcohol, with the result that they are so badly 

 distorted as to prevent certain identification. Measurements of the 

 single well-preserved specimen are : 



Length 27 mm. 



Width 8. 5 per cent of length. 



Tail: 



Length 24. 5 per cent of length. 



To central ganglion 68. per cent of length. 



Ventral ganglion (length) 4. per cent of length. 



Posterior fin : 



Length 20. 5 per cent of length . 



Width 4. 5 per cent of length. 



To anterior fin 4. 5 per cent of length. 



Proportion in front of tail-septum 77. per cent. 



Anterior fin: 



Length 23. per cent of length. 



Width 2. 5 per cent of length. 



To ventral ganglion 0. per cent of length. 



Collarette: 



Length 25. per cent of length. 



To ventral ganglion 0. per cent of length. 



Number of anterior teeth 8-7 



Number of posterior teeth 17-18 



Number of seizing jaws 8-8 



The length, number of anterior and posterior teeth, and number of 

 seizing jaws of a few other individuals are: 



The number of teeth is greater than in specimens from the San 

 Diego region (Michael, 1911, p. 45). San Diego specimens, ranging 

 in length between 15 and 26 mm., have 4 to 7 anterior, and 11 to 15 

 posterior teeth. In the Biscayan report, however, Fowler (1905, p. 

 68) records a variation in number of anterior teeth from 5 to 9 and of 

 posterior teeth from 11 to 19 in individuals between 11 and 21 mm. 

 in length. 



Distribution. — S. planktonis was collected from only seven stations. 

 Of the 84 specimens obtained, 53 were taken from below 100 fathoms 

 by open nets towed horizontally at four stations for approximately 



