86 THE VOYAGE OF H.M.S. CHALLENGER. 



septa is very irregular, and seems to proceed more quickly near the directive septa. 

 I have found that septa of the sixth and seventh orders are present in the interseptal 

 space contiguous to the directive septa, whilst septa even of the fifth order are wanting 

 in other parts. This assertion must of course be accepted with reserve, as the septa are 

 so irregularly constituted that it is difficult to determine to which order a septum 

 belongs. 



I have found the acontia only in transverse section ; they are oval filaments, dotted 

 with nematocysts, quite small, and by no means numerous. This confirms my view that 

 the acontia have hitherto been overlooked in the other species of Bunodes. 



Family, Amphianthid^e, Hertwig. 



Hexactinite, which are attached to the axial skeletons of Gorgonidse with shortened 

 sagittal and elongated transverse axis; tranverse axis lying parallel to the axial skeleton 

 of the Gorgonia ; circular muscle mesodermal ; the principal septa only perfect and sterile. 



Under the names Actinia abyssicola and Actinia gelatinosa, Moseley described two 

 Actiniae from the Challenger material, which agree in being attached to the stems of 

 Gorgonics which they clasp with their base. I was only able to examine the Actinia 

 abyssicola, as Actinia gelatinosa was not among the spirit specimens sent to me ; on the 

 other hand, I found two other new forms among the specimens, which resemble the two 

 species determined by Moseley both in their form and mode of life. 



All these forms differ so decidedly from Actinia mesembryanthemum that I have not 

 only separated them generically but united them into a new family, the Amphianthidae. 

 Closer examination shows that the mode in which they attach themselves has influenced 

 their organization in a very important and uniform manner. All the Amphianthidae are 

 elongated, corresponding to the form of the body to which they are attached, and 

 placed in such a way that their transverse axis is greatly prolonged and runs in the 

 same direction as the longitudinal axis of the Gorgonia, whdst their sagittal axis is very 

 much shortened, and crosses the skeletal axis at right angles. The oesophagus 

 consequently differs from that of other Actinise, as it is either round or even fissure- 

 shaped in a transverse direction (PI. III. fig. 7, a), and its oesophageal grooves lie so near 

 one another that they almost touch (PI. II. fig. 13). 



The internal anatomy recalls that of the Sagartidae. The six pairs of principal septa 

 are sterile and alone reach the oesophagus ; their interlying interseptal spaces have been 

 modified by the elongation of the form in such a way that the four spaces belonging to 

 the broad sides are more extensive than those belonging to the narrow sides. I was not 

 able to make out any acontia. The circular muscle is powerful and Hes in the mesoderm. 



Two species already described by other naturalists, Actinia s. Catherines and 

 Gephyra clohrnii probably belong to the family Amphianthidae. The former, which 

 was described and figured by Lesson (Voyage de la Coqmlle, Zoo!., tome ii. part ii. 



