26 BRITISH FOSSIL CORALS. 



towards the basis, rather prominent ; and subcristate near the calice, covered with 

 granulations, which become much larger towards the calice, and varying in number (1 7 in 

 one specimen, 18m another, and 22 in a third); about two thirds of them begin at the basis 

 of the corallum, and the others about half way up towards the calice, but all are of the same 

 breadth ; the position of these younger costae does not appear to be constant, for some are 

 separated by three longer ones, and others by two, or only one ; in general, however, two 

 long ones are placed between two short ones, so that the latter are only about half as nume- 

 rous as the former. The calice is nearly circular, or slightly elliptical, and the fossula appears 

 to be deep ; we are also inclined to think that there is no columella, and that the septa are 

 free all along their inner edge, but the calice being clogged up with carboniferous matter in 

 all the specimens that we have seen, we have not been able to determine these points with 

 any degree of certainty. The mode of arrangement of the septa is quite abnormal ; three 

 vertical plates advance from each of the costae towards the centre of the visceral chamber ; 

 they are all extremely thin, broad, somewhat flexuous, free from all adherence among 

 themselves, and rendered echinulate laterally by a few prominent granulations ; the plate 

 placed in the middle of each of these groups is rather thicker than the others, and the 

 space existing between it and the latter is rather larger than that comprised between the 

 lateral laminae of two neighbouring groups. Height of the corallum, about four lines ; 

 iong axis of the calice, three lines and a half; short axis, two lines and a half; breadth of 

 the costae, more than half a line. 



The three specimens of this species, from which we have drawn up the preceding 

 description, belong to Mr. Bowerbank's palaeontological collection, and were found at 

 Highgate ; Mr. Prestwich has met with it also at Clarendon Hill. 1 



Dasmia Sowerbyi is the only known species of this genus which by its general 

 characters appears to be closely allied to the family of Turbinolidae, but differs from it, 

 and even from all the other Zoantharia, by the abnormal structure "of the septal apparatus : 

 when our attention was first called to this point, we endeavoured to explain the mode of 

 radiation of the calice by supposing that each of the laminae corresponding to the middle 

 of the costae belonged to one cyclum, and that the two lateral laminae of two neighbouring 

 groups, corresponding to the two sides of each intercostal furrow, represented the two 

 halves of septa belonging to another cyclum ; 2 the slight difference in the thickness of the 

 middle and the lateral laminae, as well as the facility with which the two constituent plates 

 of the septa separate from each other in some Corals, had induced us to admit that this 

 structure was only an exaggerated form of that which is frequently met with in certain 

 Turbinolidae, in many species of Flabellum, for example, where the line of junction of the 

 two laminae that constitute each septum is indicated externally by a single costal ridge. 

 But a more attentive study of this singular fossil has made us change our opinion, and 



1 Journ. of the Geol. Soc. of London, vol. iii, p. 368. 



2 Monogr. des Turbinolides, loc. cit. 



