228 ABYLOPSIS ESCHSCHOLTZIl. 



and the subumbral canals of the nectosac. In each species there are five well- 

 developed basal teeth, one dorsal, two lateral, and two marking the dorsal wall 

 of the hydroecium. But while in A. eschschoUzii these are symmetrical, except 

 that the right hydroecial tooth is somewhat larger than the left one (Plate 14, 

 fig. 3), in A. tetragona they are so asymmetrical that it is only by tracing out the 

 ridges with which they are connected that their essential orientation can be 

 determined (Plate 14, fig. 8). The hydroecium also is diagnostic. In both it 

 is covered over by two lateral wings, but whereas in A. eschschoUzii the right 

 hand wing bears three prominent teeth near its base, and the margin of the 

 left hand wing is entire (Plate 14, fig. 2), in tetragona the right wing is only 

 slightly serrate on its transverse basal margin, while the left hand wing is toothed 

 throughout its length (Plate 14, fig. 7) instead of being entire. The most 

 important diagnostic feature of the posterior nectophore is afforded by the 

 canals of its nectosac, for while these are of the usual radial type in A. esch- 

 schoUzii, in A. tetragona they follow a very peculiar course (Plate 14, fig. 7). 



Stem and appendages, and free Eudoxids. In the oldest cormidia which are 

 still attached to the stem the bract (Plate 14, fig. 4) has already assumed its 

 characteristic pentagonal outlines; and though it still shows evidences of im- 

 maturity, it already agrees with the free Eudoxids (Plate 15, fig. 1) not only 

 in the essentials of facets and ridges, but even in such a trivial feature as the 

 presence of a tooth on the basal hydroecial margin on either side. The dorsal 

 facet is already of the regular pentagonal form, so characteristic of the free 

 Eudoxid. The serration of the ridges, prominent at this early stage, is pro- 

 gressively lost, a fact I have been able to observe on several specimens of 

 slightly different ages. 



The somatocyst has already assumed its final form; and the gonophore, 

 except for its small size, shows the structure characteristic of its later stages. 

 Indeed, the re.semblance between these cormidia and the free Eudoxids is so 

 close that there is no doubt of their genetic connection. The latter agree so 

 well with the account given by Lens and Van Riemsdijk that no account of them 

 is necessary here, further than to point out that they are easily distinguished 

 from the Eudoxids of A. tetragona by the regular pentagonal outlines of the 

 dorsal facet, by the proportionately shorter anterolateral and the proportion- 

 ately longer posterolateral facets. (Compare Plate 15, fig. 1, 2.) The form 

 of the hydroecium is likewise different in the two, and connected with it, the 

 ventral facet is basally deeply concave in eschschoUzii instead of entire as in 

 tetrago7ia. 



