25. 



27. 



This CI is an irrei^ular pentagon (textfig. 27 «, c, c, c\ e" 

 its point e). This facet is bent, the curve being about the middle 

 between ridge e and e" . It is situated nearly above the h\droecial 

 cavity and the somatocyst and constitutes the hind facet of the 

 superior nectophore. Between facet CI and A is the hydroecial 

 cavity, which for convenience's sake will be called B (textfig. 28). 

 This cavity is bounded by the inferior ridge of the paired facets 

 (ridges _/", /') and by one of the ridges of facet A, that is to say 

 ridge i. These are the odd facets. The paired ones are three in 

 number, F, F', G, G', H, H'. F and F' (textfig. 29) are rhomboids, 

 they are in connection with facet E through ridge /§, apically with 

 facet D through ridge c, with facets G and G' through ridge /, 

 with facets H and H' throusjh /;/, with facet A throug-h ridge //. 

 These facets are situated on the lateral sides of the nectosac and 

 cover a part of the hydroecial cavity. 



Facets G and G' (textfig. 30) are much smaller, small 

 trapezoids and consist of four ridges. They are connected with 

 facets F and F' through ridge /, through ridge b with facet D, 

 through ridge c" with facet CI, through ridge n with facets H 

 and H'. They overlap partly both .somatocyst and hydroecium. 

 Facets H and H' (textfig. 31) are bounded by ridge n to the 

 facets G and G', through ridge ni to facets F and F', through 

 ridge /' to facet CI while its basis constitutes the limit of the 

 hydroecial cavity B. 



All these facets are to be found in the same order in all 

 the superior nectophores of Abyla trigona which were brought 

 home by the Siboga. 



In all nectophores the stem with appendages was either 

 lost or very badly preserved. Also in this respect the material of 

 the Siboga proves to be far complete. 



As to the history of Abyla trigona we thought it necessary 

 to note the following. Ouoy and Gaimard described 27 a new 

 genus Abyla with the species trigona. Their description is unsuf- 

 ficient. They speak of "un corps tres irregulier, taille a facettes, 

 "plus long que large" etc. speaking of the superior nectophore 

 but they give no further details concerning the position of these 

 facets. Their sketches too are not quite clear. 



We had the occasion, thanks to the kindness of Prof. Edmond 

 il^g. 24-3.. .-//y/« /w.«„«Q. etc.. Facets of the superior nectophore. Perrier, to examine all the material of 



I'ig. 24: facet A, Fig. 25: facet K, Fig. 26: facet D, Fig. 27: facet CI. SiphotlOphoreS,Vj\\\c\\ fomiS [jart of the MuSCC 

 Fig. 28: Aperture of the hydroecial cavity B, Fig. 29: facet F (F'), 



Fig. 30: facet G (CO, Fig. 31: facet II (H'). Figg. 24—31: X 6- dTiistoire Naturelle in Paris. We saw some 



/ 



30. 



