THE CH.ETOGNATHA. 



69 



Sagitta bipunctata, Quoy & Gaimard. (Pi. 5. jBgs. 2S-31.) 



Characiers.—lB.eiid small; body slender, the middle third nearly of the same thickness 

 throughout, tapering slightly to\^ avds the head, more sharply towards the tail. Body 

 when preserved firm, not flabby. Longitudinal muscles broad, but not stout ; lateral 

 fields of medium development ; tlie sides of the Ijody often shrinking inwards in 

 preserved matei'ial, so as nearly to conceal the anterior fins. Tail very slender. 

 Posterior fins fairly long, more on the body than on the tail, widest nearly opposite the 

 septum; shorter than in serratodentafa, and not extending backwards nearly to the 

 vesiculse seminales. Anterior fins Aveli separated fi-oni the posterior, very narrow, not 

 reaching to tlie ventral ganglion, shorter and narrower than the posterior. Tail-tin 

 rounded posteriorly. 



Jaws strong, sharply curved in the distal half. Teeth broad below, closely apposed, 

 rather short and stumpy. Vestil)ular ridge with very slight prominences, about the 

 same length as the posterior row, projecting markedly at its external end *. 



Posterior 



teeth. 



13 



18 

 13-17 



15 



14 

 10-12 



12 



10 



A curious feature of the collection was the scarcity of this species, although, if the 

 [determinations of some earlier ol)servers are to be trusted, a plentiful supplv mi"-ht have 

 jbeen expected. The explanation is prol)ably correctly given by Stcinhaus f in saying 

 jthat this " ist keine rein pelagische Porm, ihr Vorkomnien beschriinkt sich auf die 

 Kiisten. Weun sic trotzdem auf hoher See vereiuzelt angetrolfen wurde, so ist dies^vohl 

 [dadurch zu erklaren, dass sic mit der Stromuug so weit vom Laude abgetrieben ist." 



On the other hand, during the homeward voyage, a haul in about 10 fathoms on 



* Only traces of the corona were retained iu my specimens. A good figure is given by Hertwig, Jen. Zeitschrift, 

 1880, pi. iv. fig, 20. 

 t Op. cit. supra, p. 28. 



