186 THE VOYAGE OF H.M.S. CHALLENGER. 
identical with Bathyactis symmetrica. If so, the name Fungiacyathus will take 
priority. Fungiacyathus fragilis agrees with Bathyactis symmetrica in all respects 
excepting that it has no synapticule. In some of the Challenger specimens there are 
very few synapticule indeed, but in none are these structures entirely absent. I there- 
fore hesitate to place the two forms together at present. There can be little doubt that 
they are closely allied, and what little I have seen of the soft parts of Bathyactis sym- 
metrica goes to confirm such an opinion. 
Bathyactis symmetrica, Moseley (Pl. X. figs. 1-18; la-13q). 
Fungia symmetrica, Pourt., Deep-Sea Corals, p. 46, pl. vii. figs. 5, 6. 
. ary ta } . ar 
This coral was dredged by the Challenger in all parts of the world. It varies very 
much in size and appearance, the smallest specimens obtained measuring 3 mm., and 
the largest 40 mm. in diameter: the increase in size being evidently not a matter of age 
and growth so much as of different development under different conditions. A specimen 
Bathyactis symmetrica (Moseley). 
Three times the natural size. Dredged west of Tristan da Cunha Island, from 1900 fathoms. Station 133. 
measuring only 5 mm. in diameter has already its full amount of septa. In Pourtalés’ 
specimens, the number of zones of synapticulae were from four to six. In the very 
largest specimens they only number about eight. I have figured a long series of 
specimens on Plate XI., in order to show the various forms assumed. The inspection 
of the series leaves no doubt as to the identity of the large specimens with the small 
ones. The very large specimens are excessively thin and fragile, and only a small per- 
centage of them were obtained in an unbroken condition. In some specimens dredged 
on a siliceous bottom composed of diatom skeletons, the wall is excessively thin and, 
