MADREPORARIA OF THE DEEP SEA. 323 
and they break the hard parts by their post-mortem contraction. I have only one 
small young perfect specimen out of many scores of large individuals. Consequently 
the species must be considered provisional. 
It is a common form in the Norwegian and North Atlantic Seas, and has not yet 
been found in the Mediterranean or south of the British Channel. It is evidently the 
link between the genus Mabellum and Desmophyllum. 
The species is found in the older Pliocene of Rometta. 
Genus Ruizotrocuus, Ed. & H. 1848. 
RHIZOTROCHUS AFFINIS, Duncan. (Plate XLVII. figs. 17-19.) 
The corallum is covered with a stout, well-developed epitheca. The radicles are well 
developed. The wall is very thin. The cost barely exist. The septa are slightly 
exsert, unequal, wavy, and granular. There are four cycles of them, and part of the 
fifth also. Calice most elliptical in old specimens, circular in the young. Height of 
corallum ;8;inch. Locality: Mediterranean. No. 50a, 152 fathoms. 
The reasons for associating the next genus (Amphihelia) with the Turbinoliacee in 
a new group (“those increasing by gemmation”) are given at the end of the description 
of the species. The position of the genus amongst the Oculinidew can no longer be 
maintained. 
Division GEMMANTES. 
Genus AmpuineLia, Milne-Edwards & Jules Haime’. 
The genus is differentiated as follows by its founders :—‘* Le polypier est dendroide 
et résulte d’une gemmation alterne et distique. Le ccenenchyma prend beaucoup de 
développement dans les branches basilaires. Les polypiérites sont 4 peine costales au 
bord des calices. La columella est rudimentaire ou nulle. II n’existe jamais de palis. 
Les cloisons sont peu nombreuses, entiéres, et débordent faiblement la muraille.” 
The typical form is the “white coral” Madrepora oculata of Linneus; and M. 
Milne-Edwards states that it has a rudimentary columella, the surface of the wall 
striated here and there, and that there are three cycles of septa, the primary being 
slightly exsert and projecting outwards. 
Their second species, Amphihelia venusta, has no columella, and three cycles of septa. 
There are short costal ridges near the calices, which are deep. The branches tend to 
develop on the same ventral plane. 
M. Seguenza has described some fossil species from the Sicilian Tertiaries. 
Amphihelia miocenica, Seg. It has a distinct columella; and the wall is deeply 
striated and closely granular. 
Amphihelia sculpta, Seg. It has no columella, but has cristiform cost ; and the striz 
are flexuous, anastomosing, and closely granular. 
’ Hist. Nat. des Corall. vol. ii. p. 119. 
