196 



THE VOYAGE OF H.M.S. CHALLENGER. 



SynojJsis of the Eight Families of ' Physonectse. 



Physonect^e MONOGASTRiciE, with a single 

 siphon and a single tentacle (Sipho- 

 stelia). 



Siphosome with a 

 long tubular stem, 

 longer than the 

 axis of the necto- 



Phybonmt* poly- s . ome , ( Maer °- 



GASTRICiE, With 



numerous siphons, , 



each of which is 



provided with a 



tentacle. 



biphosome with a 



short vesicular 



stem, shorter than 



the axis of the 



nectosome (Bra- 



chystelia). 



Nectosome with a corona of , nectophores, 

 without bracts, ..... 



Nectosome with a corona of bracts, without 

 nectophores, ..... 



Nectosome biserial, 

 with two opposite 

 rows of necto- 

 phores. 



Pneumatophore with- 

 out radial pouches. 

 Tentacles simple, 



Pneumatophore with 

 radial pouches. 

 Tentaclesbranched, 



Nectosome multiseriaL strobiliform, with 

 several spiral rows of nectophores, 



Nectosome with two, 

 four, or more rows < 

 of nectophores. 



Siphosome with a 

 corona of bracts, . 



Siphosome without 

 bracts, 



Nectosome without nectophores, instead of 

 these a corona of bracts, 



10. Circalidfe. 



11. Athoridffi. 



12. Apolemida;. 



13. Agalmidae. 



14. Forskalidse. 



15. Nectalidse. 



16. Discolabidse. 



17. Anthophysidse. 



Family X. ClRCALiDiE, Haeckel, 1888. 

 Circalidx, Hkl., System der Siphonophoren, p. 38. 



Definition. — Physonectae monogastricse without bracts, with a corona of nectophores 

 which surrounds the pneumatophore, and a corona of palpons which surrounds the base of 

 the single siphon and the single tentacle. Pneumatophore with radial pouches. 



The family Circalidae is founded by me for the new genus Circalia, and comprises 

 those monogastric Physonecta? which possess an upper corona of nectophores around the 

 apical pneumatophore, and a lower corona of palpons around the basal siphon. They are 

 similar to the polygastric Discolabidae, and may be compared to a Stephanospira which 

 has developed a single siphon only and a single spiral row of nectophores. 



The single specimen of Circalia which I have been able to examine living was 

 observed by me in September 1869 on the west coast of Norway, off the mouth of Sogne 

 Fjord ; it is figured in PI. XXI. figs. 1-4. But perhaps there belongs to the same genus 

 (or forms a new closely allied genus) another, larger, monogastric Physonect, which was 

 captured in August 1826 by Captain Dumont d'Urville in the Atlantic Ocean (lat. 

 30° S., long. 15° E.). It is described and figured by Quoy and Gaimard under the name 

 JPhysophora alba. 1 L. Agassiz afterwards established for it the genus Haplorhiza (a 

 name previously employed for a Rhizostomid) (36, p. 368). According to the description 



1 Voyage lie "!' Astrolabe " (Zoophytes), p. 53, pi. i. figs. 1-9. 



