548 B,. F. Tomes — Some Cretaceous Madreporaria. 



denticulated, and some of the newer rnn into the older ones. The 

 cycles are not traceable on account of the centre of the calices being 

 more or less filled up with extraneous matter, but there are about 

 forty septa. 



The continuity of the septa between the calices of this species 

 gives it a somewhat Thamnnstrcea-WXie aspect, which is suggestive of 

 the presence of pseudo-synapticulee. These, however, I have been 

 unable to detect. 



Diameter of tlie corallum, about 1 inch 9 lines. 



Height of the corallum, about 1 1 lines. 



Diameter of the calices, from 1| to 2 lines. 



Genus Rhizangia, Edw. and Haime, 1848. 

 Fodoseris, Duncan, 1869. 



My acquaintance with the corals of the Red Chalk dates from 

 1862, when, with other members of the British Association, then 

 met at Cambridge, I visited Hunstanton and secured a considerable 

 number of specimens. At that time I obsei'ved the peculiarly 

 expanded base, with its ragged outline, suggestive of incompleteness, 

 which characterizes so many specimens. Again in 1876, when a 

 considerable collection of these small corals came into my possession, 

 I was similarly impressed with the appearance presented by the 

 peculiar conformation of the base, notwithstanding that Prof. Duncan 

 had in the interval made the species the type of a new genus, under 

 the name of Fodoseris. But it was not until the kindness of Dr. W. 

 Bolsche had furnished me with specimens of Rhizangia Sedgwicld, 

 from the Cretaceous deposits of Gosau, that the real affinities of the 

 Hunstanton corals became manifest, and their identity with Bhizangia 

 established. 



The comparison of the Hunstanton corals with undoubted examples 

 of that genus, besides detecting characters which have led to the 

 generic alterations here made, has also been the means of discovering 

 some other peculiarities which deserve mention. The endotheca of 

 the species described by Prof. Duncan under the names Fodoseris 

 mamiUiformis and Fodoseris elongata is peculiar, and cannot be 

 understood without the assistance of vertical and hoi'izontal sections. 



The septa, like those of Cyclolites and Leptophyllia, are formed by 

 ■vertical trabiculae, having schlerenchimatous expansions at regular 

 intervals, constituting horizontal ledges, which are on the same level 

 on each side of the septum, but are not opposite those of other septa, 

 and they do not meet in the middle of the loculus. Dissepiments 

 are present, but they are peculiarly arranged. At nearly regular 

 intervals from the base of the corallum upwards, there are thick and 

 rudely-formed layers of endotheca. which are of a dissepimental 

 nature. They extend in all the loculi across the whole of the corallum, 

 on nearly the same level, and are formed by the crowding together 

 of numerous thin and flat dissepiments. Their position in the 

 corallum is indicated in Prof Duncan's figure of Bhizangia elongata. 

 (Supp. Brit. Foss. Cor. pt. ii. pi. ix. fig. 16). Magnified representa- 

 tions of the same are also given in Figures 9 and 11 of Plate XIV. 

 accompanying the present paper. 



