404 bulletin: museum of comparative zoology. 



is correct, Vogtia and Hippopodius being actually separable, not by 

 the form of the gonophores, but by a much more important character, 

 structure of the tentilla. In Hippopodius, as has long been known, 

 these organs, when adult, consist of a large, sac-like cnidosac (Plate 7, 

 fig. 7), with single terminal filament. And this state is attained by a 

 direct development (Plate 7, fig. 6). In Vogtia, it is true, the adult 

 tentillum (Plate 4, fig. 7; 1911b, Plate 15, fig. 7) resembles that of 

 Hippopodius superficially. But in its development it passes through 

 a spirally coiled stage (Plate 4, fig. 6), closely resembling the tentilla 

 of certain agalmids. And the apparent cnidosac of the adult tentillum 

 of Vogtia is in reality the spiral cnidoband of the younger tentillum, 

 shortened and flattened into one plane; i. e., a secondary, not a prim- 

 ary development. The difference between young tentilla of the two 

 genera is very striking. 



The new hippodid described (p. 407) has tentilla of the "Vogtia" 

 type, though its nectophores are rounded, like Hippopodius. And 

 as the structure of the tentillum is undoubtedly far more important 

 in phylogeny, and hence classification, than the mere details of outline 

 of the nectophores, it follows that the latter can no longer be used as 

 a generic character in this connection. 



Hippopodius hippopus (Forskil). 



Plate 7, fig. 6, 7. 



Gleha hippopus Forsklil, 1775, p. 14; 1776, pi. 43, fig. E. 

 (For synonymy, see Bigelow, 1911b, p. 208). 



This well-known siphonophore was 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, 10,184, 10,186, 10,187, 10,188, 10,192, 10,194, 10,195, 10,197, 

 10,198, 10,200, 10,202, 10,203, 10,207, 10,208, 10,209, 10,210, 10,211. 

 Some of the captures were made on the surface, most of them, how- 

 ever, in open-net hauls from 100 fathoms, or more. Thus it was 

 almost universal in the warm waters traversed by the Bache, failing 

 to appear at only 8 out of 37 tow-net stations. But it did not occur 

 in the cool coastal water off Chesapeake Bay (Stations 10,157-10,160). 



Hippopodius hippopus has so often been recorded, and is so well 

 known, that no account is needed here, further than to point out that 

 none of the spherical larvae, or primary bells, of this species, so 

 characteristic and easily recognized (Chun, 1897a), were detected in 

 the Bache collections, though they outnumbered the adults in the 



