BIGELOW: MEDUSAE AND SIPHONOPHORAE 423 



10,198, 10,200, 10,203, 10,208, 10,209, 10,211, 10,212; both in surface 

 and intermediate hauls. The series consists of about 200 necto- 

 phores, mostly superior. Moser's (1912b) figures of successive stages 

 in the development of D. dispar prove conclusively that the Doro- 

 masia pida Chun is merely a young stage of D. dispar, as I have 

 already suggested (1911b, 1913). 



It was hardly to be expected that these rather fragmentary necto- 

 phores would add anything to our knowledge of the morphology of 

 this species. But in as much as the presence of a set of teeth on the 

 dorsal aspect of the dorsal wall of the hydroecium is characteristic of 

 D. bojani (p. 425), I may emphasize that this region is perfectly smooth 

 in all specimens of D. dispar which I have examined. 



DiPHYOPSis MiTRA (Huxley). 



Diphyes mitra Huxley, 1859, p. 6, pi. 1, fig. 4. 

 (For synonjony see Bigelow, 1911b, p. 258). 



Diphyopsis mitra proved to be one of the commonest siphonophores 

 in the collection, being taken at Stations 10,161, 10,162, 10,163, 10,166, 

 10,169, 10,171, 10,172, 10,173, 10,176, 10,178, 10,180, 10,182, 10,186, 

 10,187, 10,192, 10,194, 10,195, 10,197, 10,200, 10,203, 10,207, 10,208, 

 10,209, 10,211, 10,212; in both surface and intermediate hauls. The 

 material consists of upwards of 400 superior nectophores, all more or 

 less fragmentary. 



It is surprising that a species as well characterized and as common in 

 the warmer parts of the Atlantic as is D. mitra should so long have 

 been overlooked there, its first definite record from that ocean being 

 in 1911 (Bigelow, 1911b, p. 259). Since that time, however, it has 

 been found in numbers not only among the West Indies and in the 

 region traversed by the Bache, but widely distributed over the 

 tropical Atlantic (Moser, 1913a). 



Its size and general outlines are such that it has probably been often 

 confused with D. appendic^daia. Hence though it is in reality one of 

 the most easily recognized members of the group, and has already been 

 described and figured by me in detail (1911b), its diagnostic features 

 are briefly summarized below. 



The diagnostic characters of the superior nectophore are its high, 

 symetrically pyramidal, form, with five ridges running from apex to 

 base; small dorsobasal, but no laterobasal teeth; hydroecium longer 

 below than above the opening of the nectosac, truncate at its apex; 



