MADEEPOBAEIA OP 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 Norv^egian and North Atlantic Seas, and has not yet 

 been found in the Mediten-anean or south of the British Channel. It is evidently the 

 link between the genus Flabellum and Besm&phyllum. 



The species is found in the older Pliocene of Rometta. 



Genus Ehizotkochus, Ed. & H. 1848. 

 Rhizotrochtjs affinis, Duncan. (Plate XL VII. figs. 17-19.) 



The corallum is covered vyith a stout, well-developed epitheca. The radicles are well 

 developed. The wall is very thin. The costee 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 ^ inch. Locality: Mediterranean. No. 50 «, 152 fathoms. 



The reasons for associating the next genus [Amphihelia) with the TurUnoliacem 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 Oculinidce can no longer be 

 maintained. 



Division Gem mantes. 



Gfenus Amphihelia, Milne-Edwards & Jules Haime'. 



The genus is differentiated as follows by its founders : — '■ Le polypier est dendro'ide 

 et resulte d'une gemmation alteme et distique. Le coenenchyma prend beaucoup de 

 developpement dans les branches basilaires. Les polypierites sont a peine costales au 

 bord des calices. La columella est rudimentaire ou nulle. II n'existe jamais de palis. 

 Les cloisons sont pen nombreuses, entieres, et debordent faiblement la muraUle." 



The typical form is the "white coral" Madrejiora oculata of Linnseus ; 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, AmpMlielia 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 mioccenica, 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 costee ; and the striae 

 are flexuous, anastomosing, and closely granular. 



' Hist. Nat. des GoraU. vol. ii. p. 119. 



