302 THE VOYAGE OF H.M.S. CHALLENGER. 



phores. Fewkes' description, however, is so inaccurate, and the examination so super- 

 ficial, that it is impossible to identify with any certainty his Angelo'psis and my 

 Auralia. 



Genus 64. Rhodalia? Haeckel, 1888. 

 Rhodalia, Hkl., System der Siphonophoren, p. 43. 



Definition. — Rhodalidae with a double or multiple corona of nectophores, arranged in 

 two or several circles. Trunk of the siphosome without proper central cavity, traversed 

 by an equal reticulum of trunk-canals. 



The genus Rhodalia, represented by the wonderful South Atlantic Rhodalia miranda 

 (Pis. I.-V.), differs from the preceding Auralia in two important characters. The necto- 

 some is similar to that of Forslcalia, composed of very numerous nectophores, which are 

 not arranged in a simple corona, but in several circles or spiral rows. The trunk of the 

 siphosome is a solid cartilaginous bulb, without central cavity, pierced everywhere by an 

 equally developed network of trunk-canals. Rhodalia, therefore, represents the most 

 highly developed genus of Auronectse. 



Rhodalia miranda, n. sp. (Pis. I.-V.). 



Habitat. — Western part of the South Atlantic, south-east of Buenos Ayres. Station 

 320, February 14, 1876 ; lat. 37° 17' S., long. 53° 52' W.; depth, 600 fathoms. 



Rhodalia miranda was preserved in rather good condition in the Challenger collec- 

 tion, enclosed in a spirit bottle, the clear spaces of which were filled by horse-hair. 

 Entangled in the latter were found the detached siphons and tentacles of the corms 

 (compare p. 290), whilst the detached nectophores were found in great numbers on the 

 bottom of the vessel. The corms themselves, as well as all their component parts, 

 were very much contracted by the action of the strong alcohol. In the living and 

 fully expanded state they are probably twice the size (or more) shown by the following 

 list of dimensions (p. 303). But the state of preservation, even of the most delicate 

 tissues, was very good, as is seen by comparing figs. 4, 5 (PI. I.), figs. 7-12 (PI. II.), and 

 Pis. IV. and V. 



Size. — The diameter of the entire corm was in three of the preserved specimens, 

 on an average, between 40 and 50 mm., in the fourth smaller specimen 30 mm. The 

 largest specimen preserved, which is figured in Pis. I. III., twice natural size, gave the 

 following maximum dimensions in millimetres : — 



1 Rhodalia = Sea-rose, poSo>, ahtav. 



