17 



main differences are that in bipunctata the posterior fin is rather more on the trunk than on 

 the tail, the corona extends on to the head, and the papillae of the vestibular rido-e are less 

 developed, than in neglecta. For a comparison of the armature in cases of doubt there follows 

 a table of formulae of small bipunctata from Parson's Bank in the English Channel: 



io.o 20 8 4 8 



9.0 22 9 5 10 



8.0 25 8 3—5 7—10 



7.5 26 849 



5-o 28 8 4 8 



6.0 25 — 28 7—9 3—4 5 _8 



5-5 27 8 3 4—5 



It will be obvious how closely these figures approach neglecta at about 7 to 8 mm. of total 

 length, especially as Aida records 8 jaws for neglecta. 



It seems very unlikely that the biptmctata of Beraneck was referable to Ouoy and 

 Gaimard's species. Amboina, whence it was obtained, is near to the centre of the area studied 

 by the Siboga, from the collections of which it appeared to be absent; the expedition could 

 hardly have missed it systematically for a whole year. As already mentioned, except with 

 formalin specimens before one for comparison, it would be extremely difficult to distinguish 

 between neglecta and small bipunctata, and attention had not been called to the former when 

 Beraneck wrote. He records only one or two details; the length of 13 mm. is rather more 

 than that noticed in the Siboga neglecta ; but his description of the epidermic thickening at the 

 neck (collarette) recalls neglecta much more than biptmctata ; it can hardly be said that the 

 slight thickening in bipunctata O. G., "etablit une transition entre les Sagitta et les Spadella", 

 but this might fairly be said of neglecta. 



7. Sagitta pulchra Doncaster. 



L. DONCASTER. The Fauna and Geography of the Maldive and Laccadive Archipelagoes. 

 Vol. I., part 2. The Chaetognatha, p. 213. 



Characters. Head rather small; behind it a distinct collarette. Body slender, nearly 

 as transparent as in enflata, but firmer. Trunk thickest at about one-half to three-quarters of 

 the distance between head and tail-septum; tapering rapidly to the septum, more gradually 

 forwards. Longitudinal muscles slight, but stronger than in enflata; lateral fields large. Tail 

 about 18 to 27 per cent, of the total length. 



Anterior fins long, commencing at the ganglion, broadest just before their posterior 

 end; consisting anteriorly of an epidermic thickening without, or with few, rays. Posterior fins 

 shorter, very nearly meeting the anterior, rather more on the trunk than on the tail, broadest 

 at or behind the plane of the septum, hardly reaching the vesiculae seminales. Tail fin 

 slightly rounded. 



SIBOGA-EXPEDITIE XXI. 3 



