2GG ARCHISOMA NATANS. 



out that the second bells of undoubted Diphyids may first appear at a late stage, 

 i. e. in D. mitra (p. 260). 



The collection contains a single large Eudoxid which can not be located 

 in its proper systematic position until we know from what polygastric form it 

 is liberated. In the form of the bract and of the gonophore it differs widely 

 from any other Eudoxid yet known, and since the animal must have some name, 

 if only for convenience sake, it may be called Archisoma natans. Whether or 

 not this name proves permanent will depend, of course, on whether the poly- 

 gastric state has been described, or whether it is as j^et unknown. The rounded 

 form of the bract suggests that the Eudoxid in question belongs to some Prayid, 

 possibly to Nectodroma reticulata. Such a connection is also suggested by the 

 structure of the somatocyst. 



ARCHISOMA, gen. nov. 



Archisoma natans, sp. nov. 



Plate 20, fig. 6. 



Station 4719. 300 fathoms to surface. 1 specimen in good condition. 

 Type. 



In the single example the bract is of the remarkable length of 37 mm. 



Bract. The soft transparent bract is greatly elongate both above and 

 below the point of attachment of the stem. Anteriorly it is pyramidal, ending 

 in an acute point, but with rounded edges. Posteriorly its dorsal face is rounded, 

 its ventral face so deeply furrowed, that it encloses a well-marked hj'droecial 

 groove which is deepest proximally. The bracteal canals (somatocyst) follow 

 an unusual course. Two main trunks arise at the usual point of origin, one 

 ascending, the other descending. The former follows a somewhat sinuous 

 course to the apex of the bract, giving off a single transverse branch which extends 

 to the dorsal surface. The descending trunk, shortly after its origin, branches 

 dichotomously, the two resultants running along the two sides of the hydroecial 

 groove. But instead of continuing independent, the two canals reunite at the 

 end of the hydroecium, to run as a single vessel to the extremitj' of the bract 

 (Plate 20, fig. 6). 



Nectophore. The special nectophore, like the bract, is very large (15 mm. 

 long) and is of a characteristic form. Apically it is rounded, but basoventrally 

 it is prolonged in a narrow conical prominence, just above which lies the mouth 

 of the nectosac. Bract and nectophore together form an "arrow head." The 

 canal sj'stem of the nectophore, like that of the bract, is complex. 



