REPORT ON THE ACTINIARIA. 67 



they are not of the same size, become smaller in proportion as they belong to the more lately 

 formed intraseptal spaces. Neither of these rules applies to Polysiphonia tuberosa. A 

 glance at fig. 9 (PL 11.) shows at once the differences which take place in one and the same 

 circle, and if we go into the relations with the intraseptal spaces, we find that the twelve 

 largest tentacles open into the twelve primary and secondary intraseptal spaces, whilst 

 the smallest of all the tentacles belong to the twelve tertiary intraseptal spaces. In 

 Polysiphonia the principle which regulates the size of the tentacles may be included in 

 the proposition, that the tentacles become smaller the further they are removed from the 

 twelve large tentacles of the first and second orders. 



The oesophagus is tough and thick walled like the oral disk, whilst the septa are thin 

 like veils ; the oesophageal grooves and longitudinal furrows require no special description. 

 Of the forty-eight pairs of septa twenty-four are perfect, but the state of preservation of 

 all the internal organs of the species was such that I can say nothing as to the structure 

 and arrangement of the reproductive organs. 



Polystomidium, n. gen. 



Liponemidse, with longitudinal furrows and marginal spherules on the wall ; tentacles 

 transformed by retrograde formation into stomidia ; circular muscle endodermal. 



In the Polystomidia, the tentacles have imdergone retrograde formation to an extent 

 which has hitherto been observed only in the genus Polyopis; the only traces of them 

 are the tenninal openings, which lead directly into the radial chambers and are surrounded 

 by swollen margins, the remains of the tentacle waU. In their habit of body, in the 

 endodermal position of the circular muscle, and in the presence of the marginal spherules, 

 these animals are allied to the Antheadae. 



Polystomidium patens, n. sp. (PI. V.). 



Body dish-shaped, widening from the small pedal disk to the wide oral disk ; stomidia 

 in two alternating rows. 



iZa6{ta(.— Station 296. November 9, 1875. Lat. 38° 6' S., long. 88° 2' W. Depth, 

 1825 fathoms. One specimen. 



Dimensions. — Diameter of the oral disk, 6 cm.; diameter of the pedal disk, I'o cm. ; 

 height of the wall, 2' 7 cm. 



Colour. — (Determined from the spirit specimen) brownish-grey, the endodermal parts 

 brown-violet, except the filaments which were coloured white. 



Of this interesting deep-sea Actinia, which I have placed here under the name Poly- 

 stomidium patens as the representative of a new genus and new species, I had unfor- 

 tunately only one specimen at my disposal, and it had been so severely injured in being 

 dredged from the depth of 1825 fathoms, that it was in a condition but little adapted 

 for minute examination. The body was flattened into a cake, of which one side was com- 



