R. F. TOMES ON THE GREAT-OOLITE MADREPORARIA. 185 



in the centre ; the third is half the length of the first -and second ; 

 and the fourth is two thirds the length of the third. 



Height of the corallmn 3^ inches, greatest diameter 3| inches, 

 diameter of the calices j inch. 



This species differs from C. burgunclioe in its globular form and 

 in having larger calices, which are much more prominent, and with 

 their centres much deeper, and the septa of the first and second 

 cycles of equal length. 



A second example of this species was found by me on the surface 

 of a field east of the Duke of Marlborough's iron-works at Fawler, 

 near Charlbury, by the side of the road leading from Pawler to 

 Stonesfield. It is of smaller size than the Fairford specimen, and 

 the septa are thinner. Otherwise the two are very similar. 



Genus Isastr^ea, M.-Edw. and Haime. 



Isastr^ea limitata, Lamx. in Mich. 



This is an abundant species at Fairford, Stonesfield, and Rollright, 

 and has been found also in equal abundance at Steeple Barton and 

 Glympton, but seems to be less plentiful at Burford, where the 

 Isastrcea explanulata occurs in great numbers. 



All the specimens in Mr. Slatter's collection have an expanded 

 form with a thin margin and a more or less gibbous upper surface, 

 and are provided with a rugged base surrounded by a strong and 

 wrinkled epitheca. But the calices do not differ from those of the 

 dendroid or foliaceous varieties which are so common in the Great 

 Oolite of Oxfordshire. 



Isastrjea MicROPHYLLA, Tomes, Proc. Geol. Assoc, vol. vi. p. 158. 



Sines the publication of the description of this well-marked species, 

 I have examined, by the kindness of Mr. J. "Windowes, of Chipping 

 Norton, a specimen from the railway-cutting at Rollright. This 

 is in a good state of preservation, and confirms the characters already 

 assigned to the species. - 



Isastr^a Beesleyi, Tomes, Proc. Geol. Assoc, vol. vi. p. 159. 



Besides occurring in the Rollright coral-bed, from which the type 

 specimens were obtained, I can now record the existence of this 

 species in considerable numbers in Mr. Slatter's collection, and add 

 Fairford as a locality where it has been found. 



Isastrcea gebbosa, Duncan, Supp. Brit. Poss. Cor. pt. iii. p. 15, pi. ii. 

 . figs. 10, 11. 



In the Stonesfield cutting this species occurs, though not abund- 

 antly, and is there associated with the allied species Isastrcea limitata. 

 The short, thick and strongly ribbed septa, shown in Prof. Duncan's 

 figure, are characteristic of this species. In all the specimens I 

 have seen, the outer ends of the septa alternate very regularly with 

 those of contiguous calices, and are never continuous with them. 



