Ilyflractinia, Parkrria, and Stromatopora. 51 



and fip^. C^^ a), comniunicating at the base with tlic interval 

 between the two laniinaj, closed at tlic summit (fip;. 4, f) ; 

 massive, but radiate in structure, the ends of the radii coitc- 

 s))ondinf^ to si-rruhited ridi^cs on the surface of the s])inc 

 {ivj^. ()), which ridi^cs diminish in number ui)wards until by 

 union they form the summit of the cone (fig. G, h). Small 

 circular apertures, about l-6()()th inch in diameter, ])lcntifully 

 scattered among the sen-ulated points of the rugged ridges and 

 bases of the large spines (fig. 5, ccc), which are the openings 

 of short tubular cavities, that respectively end in dia])hragms 

 with a small circular hole where they open into tlie interval 

 between the two laminaj (fig. 4, (jg). Dia])hragms aljout 

 5-1 sooths inch in diameter, apparently continuous with 

 the chitinous membrane lining the internal cavities, and, for 

 the most part, visible through the a])ertures on the surface. 



Hah. Marine, incrusting small univalve shells. 



Loc. Cape Palmas, Guinea coast, Africa. 



Ohs. There are two specimens of this species, viz. one on a 

 small ^^ure.r about eight twelfths of an inch long, bearing two 

 spines equally covered by the Uydractinia^ and the other on 

 a broken shell of the same size and kind. Each shell contains 

 a heiinit crab {Pagurus). They were sent to me in a dry 

 state ; and failing to obtain, by soaking in warm water, any 

 return of form in the soft parts beyond that of thread-cells, I 

 am unable to describe more than the skeleton. With the 

 exception of the skeleton being massive and not reticular and 

 chitinous, it is otherwise so like that of Ihjdractinia ccldnata^ 

 that, on a superficial view, it would, but for the colour, be 

 said to be the same species. 



Fossil IIydeactiniid^. 



We now come to the fossil species of Hydractiniidje, viz. 

 //, Michel ini and //. cretacea, Fischer — tlie former from the 

 Upper ]\Iiocene and Older Pliocene respectively, and the latter 

 from the Upper Greensand (Bull, de la Soc. Geol. de Fr. 

 t. xxiv. p. 689, 1857) ; also //. pliocena, Allman, from the 

 Older Pliocene or Coralline crag of Suffolk ; to which I can 

 add another sj)ecies from the Upper Greensand of Haldon Hill, 

 near Exeter, lent to me by my kind friend Mr. W. Vicary, of 

 Exeter, after whom I shall call it H. Vicaryi. 



Deferring ]\I. Fischer's species for the present, we shall 

 commence with H. pUocena-^ and as Dr. Allman has not entered 

 into a sufficiently detailed description of this species for our 

 present purpose, I shall describe it from the specimen to which 

 1 have before alluded, which has grown over the outside of a 



4* 



