II. Systematic. 



a. SPECIES CAPTURED BY THE SIBOGA EXPEDITION. 

 I. Genus Sagitta (sensu Langerhans 1880). 

 1 . Sagitta Bcdoti Beraneck. 



Ed. Beraneck. Les Chetognathes de la Baie d'Amboine. Revue Suisse de Zoologie. 

 Tome III, p. 137. 



Sagitta polyodon Doncaster. 



L. Doncaster. Chaetognatha: Fauna and Geography of the Maldive and Laccadive Archi- 

 pelagoes, Vol. I, p. 209. 



Sagitta bipunctata Aida [nee Quoy and Gaimard). 



T. AlDA. Chaetognaths of Misaki Harbour. Annotationes Zoologicae Japonenses. Vol. I, p. 13. 



Characters. Head rather small; neck only slightly marked when in contraction-, a 

 very slight thickening of the epidermis at the neck, but no real collarette. Body firm and 

 moderately transparent in formalin. Longitudinal muscles strong but narrow; lateral fields rather 

 large. Body thickest for about the middle third of its length, tapering slightly and gradually 

 forwards, more rapidly backwards, generally with a sudden diminution at the tail septum. Tail 

 segment about 21 to 35 per cent, of the total length. 



Anterior fins long, much widest posteriorly, and diminishing rapidly anteriorly; they nearly 

 or quite reach the abdominal ganglion. Posterior fins broader than the anterior, of about the 

 same length as the anterior; more on the tail than on the trunk, widest well behind the septum, 

 reaching nearly (? quite) to the vesiculae seminales. 



Jaws broad, not very strongly curved; tip short, thick, obtuse. Anterior teeth closely 

 set, broad below, small. Posterior teeth very numerous, narrow, very closely set; the series 

 curves from the dorsal to the ventral surface towards the mouth as in macrocephala. The points 

 of both sets of teeth small and obtuse: both have a dark brown colour in the older specimens. 



Vestibular ridge terminating externally in a well-marked rather sharp process, and pro- 

 duced into fairly regular numerous acute prominences. Corona ciliata slightly sinuous, extending 

 from a half to about two-thirds of the distance between the head and the abdominal ganglion. 



The tips of the newer jaws are in some specimens distinctly curved, but I have never 

 seen them quite so hooked as in Be'raneck's figure (PI. IV, fig. 10). The same author figures 



