36 MONOST^CHAS. 



snpracalycine nematophores, and with azygous nematophores along the 

 hydrothecal side of the ramulus. 

 Gonosome not known. 



The genus Hippurella unites in itself the characters of a Plumularia 

 and of an Antennularia or Antennopsis. Indeed, the genera Plumularia, 

 Antennularia, Antennopsis, and Hippurella differ from one another mainly 

 in the disposition of the ultimate ramuli. The characters thus afforded 

 have long been recognized as of generic value in the separation of 

 Antennularia from Plumularia, and the apphcation of the same principle 

 to other forms necessitates the construction of Antennopsis and Hippurella 

 as legitimate genera. 



Hippurella annulata. 



PL XXL Figs. 7, 8. 



Trophosome. — Hydrocaulus attaining a height of about three inches, 

 springing from a dense bundle of tubular filaments, fascicled throughout 

 the main stem, which sends off numerous non-fascicled branches, which 

 are pinnately disposed below, but given off irregularly towards the distal 

 end of the hydrocaulus; ultimate ramuli alternate and pinnate towards 

 the proximal ends of the branches, but towards the distal ends surround- 

 ing the branch on all sides, and here either scattered or regularly verticil- 

 late ; each composed of alternate long and short internodes with inter- 

 vening groups of VQYy short ring-like internodes, each of the long internodes 

 carrying a hydrotheca. Hydrothecae deep, thimble-shaped, with slightly 

 everted margin. Besides the supracalycine pair of nematophores, there 

 are two mesial nematophores, bprne by the ramulus, between every two 

 hydrothecae. 



Gonosome not known. 



Off Piuific Reef from a dei)th of 283 fathoms. 



The species is rendered striking by the large size and deep thimble- 

 shaped form of its hydrothecae, and by the annulation, at intervals, of its 

 ultimate ramuli. 



MONOSTJ^XHAS Allman nov. gen. 



Generic Cilvracter. Trophosome. — Stem branched ; hydrothecal ramuli 

 confined to one side of their supporting branches. Hydrotheci\3 unilateral 



