16 



T. AIDA. 



of the year, though the number differs according to meteorological con- 

 ditions. The length of the body when fully grown is 12mm. and its 

 breadth l.Ormn. The caudal segment is 2mm. The anterior pair 

 of lateral fins lies midway between the abdominal ganglion and the 

 posterior end of the trunk segment. The second pair is much larger, 

 and extends along the lower part of the trunk, to the middle of the cau- 

 dal segment. The eipdermis and the muscular coat are very thin. 

 The ovaries are small and scarcely reach the upper end of the second 

 lateral fin. The head is comparatively small, and has ( J-10 seizing 

 books, 6-8 anterior teeth, and 10-11 posterior teeth. The corona 

 ciliata is skein-shaped and lies on the head segment. The ratio of the. 

 length of the caudal segment to that of the whole body is, in our speci- 

 mens l / s — l fe, thus differing from that given by GrBASSl, which is 



i. Sagitta neylecta, uov. sp. 

 (Fig. 7.) 



This is the smallest sized species. The whole length of the body is 

 7mm., that of the caudal segment l.Tuim., and the breadth 0.35mm. 

 The fins are five ; the first pair of fins begin at the posterior end of the 

 ventral ganglion ; the second pair, which is separated from- the first, is 

 longer, extending to the middle of the caudal segment. Both lateral 

 fins are semi-elliptic. The corona ciliata is long, like that of Sagitta 

 bipimctata, and lies wholly on the trunk segment, never extending to 

 the head segment between the eyes. Seizing hooks 8 ; posterior teeth 

 10-12, anterior teeth 4-5. The top of each tooth has fine processes. 

 The ovaries reach the upper end of the second pair of fins. The sper- 

 matic vesicle is comparatively large. The epidermis thickens at the 

 anterior part of the trunk, as in Sagitta bipimctata. The intestine has 

 two diverticula at its anterior end. 



This species is abundant in Misaki throughout the year. 



