EEPORT ON THE SIPHONOPHORJE. 79 



comprises those small forms of the family, the vertical sail of which contains no chitinous 

 crest. The pneumatocyst, therefore, is the horizontal elliptical chitinous disc alone ; no 

 vertical skeleton crest is developed upon its surface, as in Velella and Armenista. The 

 soft vertical sail is placed in the major axis of the ellipse, not obliquely in a diagonal. 

 The species of Rataria upon which Eschscholtz founded the genus were probably young 

 larval Velellse, perhaps the same as those of which Bedot has during the last few years 

 given an anatomical description (58-62). Pagenstecher gave in 1863 a very accurate 

 description of Rataria, with historical remarks on the Velellidse in general, and discussed 

 the question whether these forms of Disconectse were only a larval stage of Velella (or 

 perhaps of Porpita) or an independent peculiar genus of this group. As a fact both 

 alternatives are true. Rataria cristata, from the Tropical Atlantic, described in the 

 following pages, and found in the Challenger collection (Station 348), is a VelelHd which 

 produces gonophores in the form of Rataria, and therefore is the representative of an 

 independent genus. The larvse of Velella and Armenista, on the other hand, all pass 

 through a larval stage similar to the former. But no Porpitidse have a similar larval 

 form, since the vertical sail is completely wanting in this family, and is only to be found 

 in the family Velellidse. Regarded from a phylogenetic point of view, Rataria is a 

 necessary intermediate link between the older Porpita and the more modern Velella. 



Rataria cristata, n. sp. (PL XLIV.). 



Habitat.— Station 348, Tropical Atlantic ; April 9, 1876 ; lat. 3° 10' N., long. 14° 51' 

 W. Surface. 



Umbrella (fig. 1, from above ; fig. 2, from below ; fig. 3, half lateral, half apical view; 

 fig. 4, lateral view ; fig. 5, frontal section). — The horizontal disc of the umbrella is elliptical, 

 4 mm. long and 3 mm. broad in the expanded state. The vertical sail which arises in 

 its sagittal or longitudinal axis, is very contractile, and therefore exhibits very different 

 forms (figs. 3, 4). The vertical transverse section of the umbrella (fig. 5) demonstrates 

 that the greatest part of its volume is occupied by the pneumatocyst (.])/), and the 

 centradenia (uc) which lies between this and the central siphon (sa). 



Exumbrella (figs. 1, 3, 4). — The superior or apical face of the umbrella is divided 

 into three parts — the vertical sail (velarium), the campanulate part, which includes the 

 pneumatocyst (pneumatophore), and the broad horizontal free border (limbus). 



Limhus Umbrellm (uu). — The peripheral border of the horizontal disc, which surrounds 

 the campanulate pneumatosaccus, is an elliptical ring of 0'5 mm. in breadth ; its outer 

 edge is densely beset with a series of marginal muciparous glands (us), and on the inside 

 of this glandular corona runs the elliptical marginal canal (fig. 10, cc), into which open 

 the numerous radial canals of the umbrella (ce). 



