74 



single specimen, I do not venture to erect a new genus on sucli negative and perliaps 

 abnormal characters. 



Pclas^ia alba (Joy and Gaimard ') has some resemblance with this form, but differs 

 from it in the great development of the head. The naturalists of the Astrolabe collected this 

 Pelagia in the harbour of Amboina. 



Anatomical Notes. 



Unfortunately I could not obtain a single specimen for examination ; and the wish to 

 preserve the specimen of the Siboga Expedition has prevented me from dissecting it. To the 

 above-mentioned notes about this specimen I may add, that the visceral mass is enveloped by 

 a rather thick whitish membrane, with the same peculiar numerous openings as has been 

 recorded in Cyinduliopsis and Glcba ; probably, respiration takes place by means of these 

 openings. The anus opens at the right side beneath the fin, and the heart is placed far back. 

 These facts comprise in a few words all I could discover about the anatomy. 



Family III. N()tobr.anchaeid.\e. 



1886. Notobrancliacidae Pelseneer, Description d'un nouveau genre de Pteropode Gymnosome, 

 Bullet. Sci. Uep. Nord, p. 224. 



As some specimens of the genus Notobranchaca have been found in the Siboga-collection, 

 I am able to complete the description, given by Pelseneer. 



Body: contracted and pointed at the posterior extremity; visceral mass not reaching the 

 aboral pole. No dorsal spot. Head broad and swollen, distinctly separated from the short neck. 



Foot: posterior lobe tapering ; anterior lobes terminating distally in an acute angle ; 

 a small tubercle between them. 



F ins: large, rounded. 



Posterior gill: three longitudinal crests, meeting at the posterior e.xtremitv of the 

 body, and extending over the posterior third of its length ; one crest is median and dorsal, 

 and bears fringes (in the adult specimen at least), the lateral crests (right and left) are simijle. 

 A lateral gill is absent. 



Buccal appendages: short, thick buccal cones of the same external appearance and 

 of nearh' the same structure as in Clione. 



Radula: strongly develojaed, with many teeth in a transverse series, but without 

 a median tooth. 



Hook-sacs: short and shallow, with a few hooks, arranged in a bunch at each side 

 of the radula. 



Jaw: absent. 



l) Voyage de rAsUol.ibe, vol. 11. p. 392, pi. 28, figs. 7 — 9. 



