44 AGLAOPHENIA DISTAIS^S. 



the same point of origin, the twin branches then directing themselves 

 forwards and remaining nearly parallel to one another. 



The hydrothecas are so closely set that the summit of each is on a 

 level with the base of the next above it. 



This species closely resembles the preceding, A. gracilis, of which it 

 may possibly be regarded as a variety. 



Aglaophenia distans. 

 PL XXVI. Figs. 1-8. 



Trophosome. — Hydrocaulus attaining a height of about four inches, sim- 

 ple, rooted by an entangled bunch of tubular filaments, fascicled below, 

 becoming non-fascicled above, and here divided into equal internodes, 

 each of which carries a pinna on alternate sides ; pinnae distant, attain- 

 ing the length of nearly an inch. Hydrothecce deep, nearly cylindrical 

 above, narrowed below ; margin crenate, with a single long tooth-like process 

 in front ; intrathecal ridge not conspicuous. Supracalycine nematophores 

 not overtopping the hydrotheca ; mesial nematophore attaining about a 

 third of the height of the hydrotheca, to which it is adnate for its entire 

 length. 



Gonosome. — Corbulje composed of niunerous pairs of ribs, which are 

 quite free from one another, each carrying a small hydrotheca near its 

 origin, and having numerous tooth-like nematophores along its distal 

 edge ; peduncle of corbula rather long, cai'rying three hydrothecre. 



Dredged oif Pacific Reef, from a depth of 283 fathoms. 



The present species is rendered very distinct by the long tooth-like 

 process on the front margin of the hydrotheca, and by its remarkable 

 open corbula?. The form of the hydrotheca is not absolutely constant, 

 and occasionally there may be seen on the same pinna with the ordi- 

 nary form others in which the narrowing of the hydrotheca towards 

 the base is much less marked. (Fig. 4.) 



The corbula?, which closely resemble those of Aglaophenia bispinosa, are 

 in the highest degree instructive, and afford a beautiful example of 

 morphological transformation. Like the corbul^e of other species they 

 are metamorphosed pinnie, but the change here undergone is of such a 

 character as to bring out very distinctly their true morphology. The 

 pinna (Fig.) 7, which is here to become a corbula, retains nearly its ordi- 



