CARYOPHYLLIACEA. ANGIADJE. 



THE WEYMOUTH CARPET-CORAL. 



Hoplangia Durotrix. 



(Sp. nov.) 



Plate X. Fig. 9.* 



Specific Character. Plates in four imperfect cycles. 

 Phyllangia Americana. Gosse, Annals N. H. Ser. 3. ii. 349. 



GENERAL DESCRIPTION. 



Corallum. Compound, increasing laterally on all sides ; low, not rising 

 above the height of the individual corallites ; incrusting rocks. 



Corallites, Formed by budding from a permanent, thin, calcareous, 

 carpet-like expansion, which spreads around the base of the parent, to 

 which each is permanently united by the inferior portion of the wall. 

 (In the specimen in my possession, four corallites of sub-equal size are 

 grouped around a parent, which has been long dead, for the inner portions 

 of its plates have been worn away.) They are cylindrical, deep, about 

 twice as high as wide, slightly inclining outwards from the common 

 centre. 



Wall. Invested by a thin porcelain-like coat of calcareous matter, 

 which appears identical with the basal carpet. It terminates above with 

 a perfectly defined, slightly everted edge, above which the wall is beau- 

 tifully white and clean, while the epitheca is dirty white, and coated with 

 a minute sponge. The epitheca shows traces of periodic growth, by a 

 succession of such everted edges not totally obliterated ; and while in one 

 corallite the edge is level with the summits of the plates, in another there 

 is at least one-fourth of the total height above the epitheca. Hence 

 I infer that the wall with the septa makes a periodic growth above the 

 last level of the epitheca, while the latter remains dormant, and that then 

 the epitheca is deposited at once around the new growth ; the wall and 

 the epitheca thus growing alternately. The wall is covered with minute 

 scattered granules, and these as well as the ribs can be discerned through 

 the thin epitheca. 



Ribs. Thin, sharp, low, in some places discernible only at the very 

 summit of the wall, in others nearly throughout : in the former case they 

 appear again from the edge of the epitheca a little way downward. 



Marked " Phyllangia Americana" in some copies. 



