A2TC) POETLAND OOLITE OF WILTS, ETC. 563 



sloping tabular synapticulae resemble those of Thamnastrcea, but 

 are not much developed *. 



Height of the corallum about nine lines ; its greatest diameter 

 one inch seven lines. 



A second specimen consists of the peduncular portion only, and 

 has the form of an ill-formed and inverted cone, the margin of 

 which presents a slightly lobular outline. 



Both these specimens were sent to me some years since by 

 the late Mr. Bean, of Scarborough, and labelled " Meandrina 

 decorata, Bean, Coralline Oolite, Malton." 



Corals from the Portland Oolite. 



IsASTEiEA obloxga, Edw. and Haime. Pol. Foss. des Terr. Paleon. 

 p. 103 (1851); Brit. Foss. Cor. p. 73, pi. xii. (1851). Plate 

 XXII. fig. 6. 



Lithostrotion oblongum, Fleming, Brit. Anim. p. 508 (1828). 



Polished specimens of this, the only coral found in the Portland 

 Oolite of this country, are extremely pretty and ornamental objects, 

 and they are to be seen in the lady's drawing-room as well as in the 

 cabinet of the geologist. In such specimens so much difference in 

 internal structure may frequently be observed, as greatly to favour 

 the impression that more than one species have been confounded 

 under the name of Isastrcea oblonga. But such is not the case, the 

 only real difference being in the state of fossilization ; and this dif- 

 ference is so great that the real characters of the species have 

 been overlooked. 



All the figures of this Coral given by MM. Edwards and Haime 

 in their ' History of British Fossil Corals,' have been taken from 

 specimens in which the stony tissues of the corallum have given 

 way to and been replaced by a dark-coloured siliceous matter, the very 

 depth of the colour of which has effectually obscured some charac- 

 teristic details of struccure. Their figure 1 / represents a specimen 

 in which the inner parts of the interseptal loculi, instead of being 

 filled with the usual light-coloured calcareous deposit, remain open, 

 and show the conformation of the septa and the dissepiments very 

 distinctly. But in this figure, as well as in the other on the same 

 plate, the outer parts of the loculi are filled with the same dark 

 siliceous material as the walls with which they are in contact ; and 

 as this dark part is not distinguishable from the wall itself, the latter 

 appears to be of twice its natural thickness. 



By selecting specimens in which the silicified corallites are less 

 deep in colour, the details of structure are more readily seen, and 

 the wall is observed to be thin, and to be lined within with a con- 

 siderable quantity of dissepimental tissue, through which the septa 



* For a full description of these peculiarly formed synapticula?, see the 

 paper by Milaschewitcb, in the twenty-first volume of the ' Palaeontographica.' 

 When seen from the outside, they exhibit a cuneiform figure, and 1 have on 

 several occasions described them as cuneiform synapticulae. 



