234 



PROF. H. A. NICHOLSON AND DR. J. MURTE ON THE 



and Haime to the Tabulate Corals, under the name of Labecliia, 

 was rather related to the Hydrozoa. " In its earliest stages of 

 growth, tins fossil consists of a very thin circular disk, with con- 

 centric lines of growth beneath, and having the superior surface 

 studded with blunt spines, which radiate from the centre, and 

 also coalesce and form continuous ridges. In this state it reminds 

 one of nothing more than the sclerobasis of the Hydrozoan genus 

 Hydractinia ; and the only difference seems to be that Lahechia 

 is entirely calcareous, whilst Hydractinia is corneous. During 

 the course of growth, the primitive disk of Lahechia is increased 

 in thickness by the addition of successive thin strata, which 

 closely conform to the subjacent fundamental crust, being ele- 

 vated where the spines are situated. As these successive layers 

 leave a small space between them, and are in themselves very 

 thin, they give rise to a false appearance of tabulae." (Lindstrom, 

 loc. cit.) Dr. Lindstrom further points out that there are points 

 of resemblance between Lahechia and the Strom atoporoids which 

 have been generally grouped together under the name of Gceno- 

 stroma ; and he therefore throws out the suggestion that the latter 

 may possibly have to be eliminated from the group of the Corals 

 to which he thought them to belong. 



Having carefully examined specimens of Lahechia, both macro- 

 scopically and microscopically, we can entirely confirm Dr. Lind- 

 strom's general description of the genus ; and we altogether agree 

 with him, that it certainly can not be referred to the Corals. 

 Thin vertical sections (fig. 5, C) show that the skeleton is corn- 

 Fig. 5. C 

 A 



Lahechia conferta, Bclw. & H. 

 A. A small specimen, of the natural size. b. A piece of the upper surface of 

 the same, enlarged, c. Portion of a vertical section under a low microscopic 

 power : a, the calcareous columns, represented as opaque ; b, the vesicular 

 tabulae ; c, calcite filHng the lenticular vesicles. 



