SYSTEMATIC AND BIOLOGICAL ACCOUNT 89 



nectophores all of which, except a few of Rosacea cymbiformis, appear to belong to one species, 

 R. plicata. 



The only allied species that I know is the common Mediterranean one, R. cymbiformis (Delle Chiaje). 

 In both species there are only four simple, subumbral radial canals, the lateral pair of which take 

 a meandering course along the edge of the nectosac. 



A (first definitive) nectophore of R. plicata from 'Discovery II ' Station 1617, shows an interesting 

 variation in the path of the lateral radial canals. Similar variations are not uncommon. This variation 

 consists of irregular cross-branches connecting the major loop of the lateral radial canal with other 

 parts of the subumbral canal-system. Sometimes only blind diverticula are seen. This variation 

 is of particular interest in connexion with the description by Leloup (1934a) of R. (Prayoides) inter- 

 media. Leloup's specimen (fig. 4A), which I select as the holotype of R. (Prayoides) intermedia 

 Leloup, appears to show a larger larval nectophore — 'larval' because there is no descending branch 

 of the somatocyst — from which projects a first definitive nectophore with deep hydroecium. In the 

 absence of any indication of the looped Rosacea type of lateral radial canal I am inclined to regard 

 this form as too much unlike R. cymbiformis and R. plicata to be included in the same genus. 



Moser (1925) described and figured a few nectophores from the Tropical Atlantic which she called 

 R. tuberculoid.. Several poorly preserved specimens of R. plicata that I have seen look rather like 

 Moser's figures, but I have never found a well-preserved one looking like these figures. I do not think 

 1 tuberculata' represents a distinct species. 



The synonymies of the two species of Rosacea, are, in my opinion, in a state of confusion, a fact 

 that is not surprising in view of the unsatisfactory nature of so many of the earlier figures and 

 descriptions. 



The first species, R. cymbiformis, was figured unmistakably by Delle Chiaje (1822, Tav. 50, fig. 3; 

 1841-4, Tav. 33, fig. 1); Leuckart (1854, pi. 11, figs. 18-24); Vo gt (^54, pi- 16, fig. 3); and Haeckel 

 (18886, pis. 31, 32), though Haeckel's figures of nectophores are poor. I know of no recognizable 

 old figures of the second species, R. plicata. 



Rosacea plicata (? Q. et G.) Bigelow, 191 1. 



The nectophores of R. plicata fall into three categories: (1) larval caducous nectophores, in the 

 hydroecia of some of which are to be found buds of (2) secondary (definitive) nectophores. Larger 

 detached nectophores of this category are the ones most commonly found, and are those figured by 

 Bigelow & Sears (1937, figs, n, 12). In the hydroecia of a few have been found buds of (3) tertiary 

 nectophores. Nectophores of category 3 have also been found detached. The species to which all 

 these specimens belong appears to be the one that Bigelow & Sears figured and described so well in 

 their 'Thor' Report (1937) on the Mediterranean siphonophores, and for which species, rightly or 

 wrongly, they used the name R. plicata Quoy & Gaimard. 



The eudoxids are large, up to 2 cm. in length, at first sight globular, and three-lobed, much as in 

 R. cymbiformis. 1 The right antero-lateral lobe in R. plicata bends round distally to the left, and in front 

 of the distal end of the left lobe — a feature not shown by Bigelow (191 1 b, pi. 2, fig. 4) in R. cymbiformis, 

 although it often occurs in that species. In the early growth-stage it can be seen that the proximal 

 side of the bract of R. plicata is convex, whilst the distal side is flattened, as in R. cymbiformis. 



One noticeable and constant difference between eudoxids of the two species is in the position, 

 on the shorter left, lateral hydroecial canal, from which the unpaired dorsal canal springs. In 

 R. cymbiformis this position is proximal to the small lateral 'spur' canal, as clearly figured by Bigelow 

 (191 1 b, pi. 2, fig. 4), whilst in R. plicata the position is distal to — in Bigelow's figure, to the left of- 

 this small lateral spur. 



1 See PL IV, figs. 6-7. 



