HYBOCODONID.E. 421 



simple, but occasionally give off a branch. The perisarc is of a papyraceous consistence, but its 

 most characteristic feature is the presence upon the larger stems of slightly elevated annular 

 ridges which follow one another at short and rather irregular intervals. They are very distinct 

 under a low magnifying power, and give rise to a sensation of roughness when the dry stem is 

 drawn through the fingers. They appear to indicate successive periods of growth, similar to 

 what takes place in Tahularia indivisa, after each casting of the hydranth, where, however, the 

 indications of periodic growth are neither so numerous within the same space nor so distinct as 

 in the present species. 



A note appended to the specimen informs us that it was brought from Coijiiiuibo by 

 M. Gaudechaud. 



EYBOCOBONIDM. 



TROPHOSOME. — Htdrocaulus developed, invested by a chitinous perisaec. 

 HTDK.iNTHS witli a proxlmal and a distal set of filiform tentacles. 



GONOSOME. — GoNOPHORES medusiform planoblasts. 



HYBOCODON, Agassis. 



Name. — ^From iljSoc, hump-backed, and kwcwv, a bell, in allusion to the unsymmetrical form 

 of the planoblast. 



TROPHOSOME. — HYDROPnTTON consisting of a simple (or branched ?) htdro- 

 CAULTJs, rooted by a filiform htdeorhiza. Hxdranths flask-sbaped, abruptly distinct 

 from tbe supporting liydrocaulus ; the proximal set of tentacles long, and forming a 

 single verticil, tbe distal set short, and arranged in two distinctly separated verticils. 



GONOSOME. — Planoblasts springing from the body of the hydranth, between 

 the proximal and distal sets of tentacles. MsDrsA at the time of liberation with a 

 deep-belled umbrella, simple-mouthed manubrium, four radiating canals, and with 

 only one marginal tentacle, which is prolonged from the distal extremity of one of 

 the canals, and is furnished with a bulbous base destitute of distinct ocellus. 



The genus Ihjhocodon Avas established by Agassiz for a large and beautiful tubularian from 



