41 



Seen from the dorsal side, with the nectosac clearly proximal, we see a most beautiful 

 uval-shaped facet (A) with two lateral serrated ridges whose course shows a very perfect convexity. 

 These two ridges do not meet at the base, for there is yet a basal ridge, standing transversely 

 on the oval. In the centre this ridge shows a slight rise. There we see an absolutely median 

 ridge, which begins at the base of the facet near the velum, goes upwards, but does not finish 

 in the apex of the oval. It looses itself quite suddenly in the gelatinous substance. This odd 

 ridge (fig. 48 a) is not serrated. In some specimens it disappears already in the lower half of 

 the oval (Cat. 122 C. fig. 48) in others in the upper half (Cat. 164 H. figg. 49, 50). 



The lateral convex ridges of facet A are at the same time the lateral ones of a pair of 

 facets B, B' (PI. VI, figg. 49, 50 i?) situated on the right and left side of the proximal facet A. 

 They are much more irregular, very concave, as their gelatinous substance is overlapped a good 

 deal by the prominent lateral ridges of facet A. They are however well-developed, their ridges 

 begin at the top, the two posterior ones having a regular concave course. These ridges are at 

 the same time the lateral ridges of the posterior or ventral facet. They differ however one 

 from another. The left lateral ridge (facet B') is clearly seen in a lateral sketch taken from 

 the left side (PI. \T, fig. 49) but the right lateral ridge (facet B) goes parallel with the course 

 of the somatocyst, about which we shall speak later. The ridge B' is therefore narrower than B 

 especially near the apex. Basally facet B' shows us a ridge, the limits of the hydroecial cavity. 

 It goes on quite pointedly at the basal part of the nectosac, then goes upwards again and 

 bends itself. Near the lateral ridges of facet A it continues into the basal one of the latter. 

 Especially there where the ridge is produced into a sharp point it is finely serrated. 



It is clear that judging from the irregularity and the position of the paired lateral facets, 

 the odd ventral one (C) is not quite median. It is twisted, beginning at the base, and then 

 proximally to the left (see PI. VI, fig. 50). The lateral ridges of this facet are serrated near 

 the basal part; the ridges continue and form the hindwall and the limits of the hydroecial 

 cavity. Near the aperture they are very much serrated. 



Interior. The nectosac has the shape such as Haeckei, 88 b describes for true Diphyes- 

 like specimens. In Cat. 164 H it is less well-preserved than in Cat. 122 C. It has a cylindrical 

 shape, very broad as the anterior wall reaches nearly the front median ridge, while the posterior 

 one is underneath half of the breadth of the paired lateral facets B and B'. The canals in the 

 nectosac were probably absolutely invisible in consequence of imperfect conservation. 



The hydroecial cavity is small (see ventral fig. 5 1 hydr.) shallow, campanulate. 



The somatocyst (figg. 49, 50 soiii.) is nearly threadlike at the top of the hydroecium. 

 This stalk-like structure widens quite suddenly into a broad, more or less club-shaped vesicle, 

 in which there are sometimes white calcareous granules. The somatocyst is never pointed nor 

 elongated at its top, but always blunt. 



In the stem and appendages nothing particular was seen, owing also to the incomplete 

 preservation. In some specimens the groups of appendages would have been well enough 

 developed to show the appearance of a bud which would become a special nectophore. But this 

 bud always failed. We have seen clearly in some specimens, the development of a gonophore 

 but never of a special gonocalyx. 



SIBOGA-EXPEDITIE IX. . 6 



