REPORT ON THE SIPHONOPHORyE. 199 



Their principal axis is longer than the transverse axis, and is directed obliquely from 

 above downwards and outwards. The dorsal or superior face is convex in the proximal, 

 concave in the distal part. The opposed ventral or inferior face is more concave, with 

 a ridge in the middle line ; from the upper or apical part of this ridge arises the short 

 pedicle which attaches the nectophore to the axial trunk. Their jelly-umbrella is rather 

 thin, but firm. The nectosac is large ; its four equidistant radial canals are of nearly 

 equal length and run in a simple curve (without loops) from the top of the subumbrella 

 (where the pedicular canal enters) towards the basal ostium ; they are here united by a 

 circular ring-canal, above the small velum. 



Siphosome. — The basal part of the monogastric corm, below the nectosome, is composed 

 of a single, very large central siphon, and a corona of numerous palpons which surround 

 its proximal base ; each palpon bears a simple palpacle, whilst the siphon bears at its 

 dorsal side a single very long tentacle, beset with a row of numerous tentilla. The basal 

 part of the siphon, immediately below the palpons, is surrounded by a corona of gono- 

 phores. The diameter of the siphosome in the expanded state is about 10 mm. 



Siphon (s). — The large central polypite, which represents the axial trunk of the 

 monogastric corm, is divided into four segments. The first and uppermost segment, 

 comparable to the pedicle of the siphons of the polygastric Siphonanthae, is a cylindrical 

 vertical tube, to which are attached three coronas ; the upper corona composed of necto- 

 phores, the middle of palpons, and the lower of gonophores. Below this follows the 

 second segment, corresponding to the basigaster, a small ovate dilatation with a thickened 

 wall full of cnidocysts. The third segment is the large spindle-shaped stomach, the 

 wall of which exhibits eight equidistant red-brown villous hepatic ridges (sh). The fourth 

 and last segment is the distal proboscis (sr), a very contractile cylindrical tube with 

 eight strong longitudinal muscle-bands. Its terminal mouth opening exhibits eight 

 rounded radial lobes (ss). 



Tentacle (t). — The single large tentacle, which arises from the base of the siphon on 

 its dorsal side, is a very long cylindrical tube, furnished with a single series of very 

 numerous tentilla (ts) ; these are simple thin lateral branches of the tentacle, densely 

 covered with small ovate cnidocysts. The structure of the tentacle is similar to that of 

 Nectophysa ivyvillei (PI. XXIII. figs. 5, 6). 



Palpons (q) and Palpacles (r). — The corona of palpons which is expanded around the 

 base of the siphosome, immediately below the nectosome, is very similar to that of the 

 Discolabidaa. It is composed (in the single specimen observed) of sixteen to twenty — 

 or perhaps more — cylindrical tubular palpons, tapering towards the two ends ; the 

 proximal end is rounded and attached by a short and thin pedicle to the axial trunk ; 

 the distal end is closed, pointed, and armed with a group of cnidocysts. From the dorsal 

 side of the basal pedicle arises a long and very movable palpacle, a thin cylindrical 

 tubule, the wall of which contains small cnidocysts. 



