THE SIPHONOPHOEA. 347 



The somatocyst is spherical or pear-shaped, and, instead of lying nearly in the longi- 

 tudinal axis of the nectophore, is transverse, a form and position constant in the entire 

 series of 73 specimens, whether Biscayan, West Indian, or Pacific. In D. snbtiloides 

 the somatocyst, thovigh short, is of the usual fusiform type, merely somewhat narrower 

 near the base, and Lens and Van Riemsdijk found no noticeable variation from this 

 type in 110 specimens. 



Stem and Appendages. — The pedicular canal of the nectosac runs almost directly down- 

 wards tlirougliout its short course to the apex of the hydroecium. In only one specimen 

 was an entire group of developed appendages still attached. This consisted of bract, 

 siphon, tentacle, and gonophore. Although the latter was sufficiently developed for 

 identification, there was no trace of any special nectophore, and it is on this evidence 

 that the species is referred to Dlphyes rather than to Diphyopsis. 



Inferior Nectophore. — None of the specimens had the second nectophore still attached, 

 but in most of them the remnants of what was apparently the pedicular canal could be 

 detected at the base of the stem, and it is on the strength of these that the species is 

 referred to the Diphyida?. There are several inferior nectophores in the collection so 

 crumpled and distorted as to be past description or identification. It is possible that 

 some or all of them may belong to I), fowler L 



The depths of capture listed above show that, though this form occurs at the surface, 

 it is most abundant between 50 and 100 fathoms, i. ^. in a temperature of about 52° F. 



It seemed to me so unlikely that a North Atlantic species with this habitat, so easily 

 recognized as the present, and so common as it appears to be, should so long have 

 escaped notice, that 1 was loth to make it the basis for a new specific name. But 

 examination of the literature of both Diphyids and Monophyids seems to leave no other 

 course open. 



From the Atlantic forms with baso-lateral teeth — for example, Diphyopsis dispar, 

 Cham. & Eys. ; Biphyes sleenstrupii, Gegenbaur ; D. serrata, Chun ; and Doromasia 

 picia, Chun, — and from the various Pacific species with this same character, to be 

 discussed in my Report on the ' Albatross ' Siphonophores, it is readily distinguished by 

 the entire lack of such structures. The Atlantic Diphyoj)sinae previously known, which 

 agree with Diphyes acuta in this respect, are D. appendiculata, Eschsch. {=seeboldii, 

 Gegenbaur, = hipartita, Costa) ; D. arctica, Chun ; D. suhtilis, Chun ; and Diphyopsis 

 hispaniana, Mayer. But from all these, as well as from Diphyopsis mitra, Huxley 

 { = D. dipliyoides. Lens and Van Eiemsdijk), and Diphyes chamissonis, Huxley, as yet 

 recorded only from the Indo-Pacific region, it is separated by the shortness and position 

 of the hydroecium, and by the structure of the somatocyst, both of which characters 

 have proved constant. Similarly, in addition to the apparent presence of an infi'rior 

 nectophore, it is separated from the monophyids Mugcjiam. kochii, "Will, and 21. utlantica, 

 Cunningham. 



Among Galeolarinse, the only species which might perhaps agree with it with regard 

 to the somatocyst is Galeolaria turgida, Gegenbaur. But in the latter the structure of 

 the hydroBcium, and particularly the two long dorsal hydroccial wings, are entirely 

 different from the condition in I), acuta. From G. truiicata, Sars, which somewhat 



55* 



