TWO NEW TYPES OE ACTINIARIA. 
149 
pore at the tip of some normal Actiniarian tentacles — but by 
what I will term sphseridia, i. e. ampullate diverticula of the 
inter- or intra-mesenterial chambers, devoid of an opening to 
the exterior, and homologous, therefore, with the imperforate 
tentacles of many genera. 
This difference appears to necessitate the formation of a new 
family of Hexactiniae, the Phialactidse, which will rank 
beside the Liponemidae, and may be defined as “ Hexactiniae, 
in which the tentacles have degenerated into sphaeridia.” The 
possibility, however, must be borne in mind that Phialactis may 
belong, not to the Hexactiniae, but to the Monauleae (should 
such a group prove to be natural), since in the one specimen 
of which transverse sections were made, only one pair of direc- 
tive mesenteries could be detected with certainty (cf. p. 150). 
With the single form only at disposal, it is better to abstain 
from even a provisional definition of genus and species. 
The animal is goblet-shaped, the cup being represented by 
an upward extension of the oral disc, the stem by the body of 
the animal, and the foot by the limbus or base of attachment 
(figs. 10, 11). The sphseridia are borne on the inside of the 
cup only, and are especially numerous round the oral cone. 
The latter lies at the bottom of the cup, and does not itself 
bear sphseridia, in its centre lies the oval entrance to the 
stomodaeum (fig. 12). 
The external dimension of the most perfect specimen are 
approximately as follows : 
Total height 
. 6 
mm 
Height from limbus to oral opening 
. 2 
a 
Height from oral opening to upper edge of cup 
. 4 
it 
Diameter of cup above .... 
. 10 
it 
Diameter of cup below (outside) . 
. 7 
D 
Diameter of body 
. 6 
)) 
Diameter of limbus 
. 10 
it 
The general structure agrees with that of an ordinary 
Actinian, the abnormal shape being produced merely by a 
considerable upward growth at the point where body wall 
(mauerblatt) passes into oral disc. The outer part of the 
VOL. XXIX, PART 2. NEW SER. L 
