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Transactions. 



agrees so precisely with the Kerrnadec forms, and in some respects is so ex- 

 ceptional, that I carefully went through all the specimens again. In only one 

 individual could I detect the anterior fin, and this quite plainly, although it 

 was folded against the body. In its extent it does not agree with Fowler's 

 figure, though he places a (?) against his statement in the text. But owing 

 to the damage done to the posterior fin, and owing to the tenuity of this 

 anterior fin, I should not presume to doubt Fowler's statement that this 

 fin extends forwards as far as the level of the ventral ganglion, though, 

 so far as my specimen shows it, the fin is of much less extent. 



Fowler refrained from naming his two immature and somewhat 

 damaged specimens, and did not even place it in a genus, though he states 

 that certain of its characters "suggest hexajptera,'''' at the same time 

 pointing out certain differences from that species. As the only genus with 

 two lateral fins is Sagitta, there is little doubt that he intended to compare 

 it with S. hexaptera, and I take the opportunity of naming it after him. 



My specimens vary from 23-35 mm. in total length, with a diameter 

 of 2-5-3 mm. Owing to flaccidity of the body, it flattens easily, and has, 

 as I have said, been crumpled. 



The head is distinctly constricted from the body ; the curved hooks, or 

 ' jaws," are 8 or 9 on each side ; in one case 8 on one side and 9 on the 

 other. They have no distinct separate tip, but the whole hook is gently 

 curved and without any serrations. 



The frontal spines, or " anterior teeth," are on 3 each side, though in 

 one case 4 on one side and 3 on the other. 



The marginal spines, or " hinder series of teeth," form a row of 3 short 

 conical spines on the sloping anterior margin of the head. 



The tail fin is in all my specimens slightly notched ; the posterior 

 lateral fin commences rather in front of the middle of the tail, and is 

 widest just behind the anus. So far as the imperfect condition allows 

 one to judge, it has ^ of its length behind and f in front of the anus. 



The anterior fin is only 3 mm. in length ; it seems well defined, and 

 I failed to see any evidence of its continuation forwards ; its anterior 

 margin is 10 mm. from the tip of the head (the ventral ganglion being 

 about 6 mm.) ; its posterior limit is 5 mm. in front of the anus — that is, 

 close to the posterior fin. 



The formula used by Fowler is — 



Total Length. 



Tail, as Percentage 

 of Total Length. 



Number of 

 Jaws. 



Number of 

 Anterior Teeth. 



Nurnbir of 

 Posterior Teeth. 



Loc. — Sunday Island. 

 Distribution. — Bav of Islands. 



Class Enteropneusta. 

 Ptychodera flava Eschscholtz. 



Willey, Q. J. Mic. Sci., 40, p. 165. Punnett, Enteropneusta, Fauna 

 Maldive and Laccadive Archip., vol. 2, pt. 2. 

 A single lacerated broken individual, found " under stones " at Coral 

 Bay, Sunday Island, July, 1908. 

 Distribution. — Indian Ocean . 



