REPORT ON THE SIPHONOPHOR.E. 71 



conectaa, or all the " Medusas chondrophorse " of Chamisso and Eyssenhardt. After- 

 wards (in 1835) Brandt separated the true Velellidaj (with elliptical disc and vertical 

 crest) from the Porpitidse (with circular disc, without crest). The Velellidae, thus 

 restricted, agree with the Porpitidse in the polygastric structure, not only the large 

 sterile central siphon possessing an open mouth at its distal end, but also each of the 

 surrounding gonostyles. These peripheral polypites, which bear the gonophores budding 

 from then proximal part, are therefore not mouthless palpons (as in the Discalidse), but 

 mouth-bearing, feeding, and digesting secondary siphons. On the other hand, the Velellidse 

 differ from the Porpitidse (as well as from the Discalidse) in the peculiar amphithect or 

 bilaterally-radial ground-form of the body, produced by the prolongation of the sagittal 

 axis, and shortening of the frontal axis ; and, further, in the development of a peculiar 

 vertical crest or sail, which arises from the exumbrella either in the sagittal or in a 

 diagonal axis. 



Eschscholtz, in his fundamental work, 1 divided his Velellidae into three genera : — 

 Rataria, Velella, and Porpita. The genus Rataria, however, was considered by the ma- 

 jority of subsequent observers to consist only of young forms of Velella. A new species of 

 Rataria, found in the Challenger collection, proved to be an autonomous genus, provided 

 with gonophores. Although the different Ratarize, described by some authors, may be 

 merely young Velellse, there nevertheless exist also Velellidae which become mature in 

 the permanent Rataria-fovm. The numerous species of the true Velella were disposed 

 in my System (p. 31) in two genera : — Velella (sensu restricto), with an ebiptical 

 umbrella and simple corona of tentacles ; and Velaria, with quadrangular umbrella and 

 double or multiple corona of tentacles. For this latter the old name Armenista (or 

 Armenistarium of Carburius, 1757) may be better retained. 



Umbrella. — The common trunk of the cormus, which corresponds to the umbrella of 

 a hydromedusoid person, is in all Velellidse a flat, horizontally expanded, and floating 

 disc, distinguished from the circular disc of the Porpitidse and DiscaUdae, firstly, by 

 its bflateral form, and secondly, by tke vertical crest or sad. Tke latter is originally 

 notking more tkan a simple longitudinal fold of tke exumbrella, and may be regarded 

 as tke primary cause of tke peculiar fundamental form. Tke tkree genera wkick we 

 kave distinguisked represent tkree different degrees or historical steps in its peculiar 

 development : — Rataria, next to tke ancestral group Porpitidse, kas an elliptical disc, and 

 tke sail placed in its sagittal plane, in tke longer axis ; in Velella the sad turns a little 

 around the vertical main axis, and comes to be situated in a diagonal axis of the disc ; 

 finally, in Armenista the disc becomes quadrangular or parallelogram-shaped. Besides, 

 a vertical crest of the pneumatocyst, as a support of the soft sail, is developed in the two 

 latter genera, but is wanting in Rataria. 



Amphithect Fundamental Form. — The peculiar fundamental form presented by the 



1 1, 1829, p. 1G6. 



