260 DIPHYOPSIS MITRA. 



in any specimen which I have seen. The nectosac extends nearly to the 

 apex. There are no basolateral teeth, and the dorsolateral tooth is very small 

 (Plate 9, fig. 4). The length of the hj^droecium below the opening of the necto- 

 sac is much greater than its extent above that level. At the top it is truncate, 

 an outline which with the short pear-shaped somatocyst, separates D. inilra 

 from other Pacific Diphyids. The somatocyst reaches only to the mid-level 

 of the nectosac. 



The dorsal wall of the hydroecium below the bell opening is divided into 

 two wings, as it is in D. appendiculata, but they are more pointed than in the 

 latter, and the left hand one invariably (?) bears a triangular secondary flap or 

 tooth (Plate 9, fig. 4, To. H ). The basolateral margins are distinctly concave. 



All the ridges of the nectophore are serrate, except near the apex. But 

 the prominence of the serrations is variable. In all these features both Eastern 

 Pacific and West Indian specimens resemble the "Siboga" material on which 

 Lens and Van Riemsdijk based their D. diphyoides, while there is such a close 

 agreement between all of these and Huxley's figures of Diphyes mitra that I 

 have no doubt of their identity with it. Huxley's specimen differs from those 

 more recently described only in being somewhat broader, in having an even 

 smaller dorsal tooth, and less concave basal hydroecial margins, divergences 

 all of which are too trivial to suggest specific difference. The supposition that 

 D. mitra is a Monophyid (Haeckel, '88b, Chun, '92), rests merely on the absence 

 of an inferior nectophore in Huxley's single and ''obviously imperfect" ('59, 

 p. 37) specimen. That this absence was accidental can hardly be questioned 

 in view of the resemblance between his figure and the undoubted Diphyids 

 of the "Siboga" and "Albatross" collections. My identification of Bedot's 

 Diphyes gracilis as a synonym of the species under consideration rests on the 

 truncate hydroecium, the short pear-shaped somatocyst, and the conformation 

 of the base (Bedot, '96, pi. 1'2, fig. 4), as well as on the form of the inferior necto- 

 phore noted below. 



Inferior nectophore. In the "Siboga" series only the buds for inferior 

 nectophores were present; and this is true of most of the "Albatross" specimens. 

 But in one this structure is sufficiently developed to identify an inferior necto- 

 phore, found loose in the collection (Plate 10, fig. 4) as belonging to D. mitra. 

 There can be little doubt about this identification, because the differences 

 between the two are only such as might be expected at such different stages in 

 growth. The more important features are that the hydroecial canal is open, 

 though covered over near the upper end bj- two flaps, of which the left one is 



