R. F. Tomes— Corals of Cricldey Eill 301 



TSASTR^A EXP ANSA, n.S. 



Many fragments of a very thin and expanded species of Isastrcea 

 were taken by myself at Crickley before I succeeded in obtaining a 

 suflSciently perfect specimen for description. By carrying away 

 some large lumps of the soft cream-coloured Coral-bed, and ex- 

 tracting with care the corals contained in them, I obtained good 

 examples of many of the species mentioned in this paper, and 

 amongst them a series of the species which I now describe under 

 the above name. 



Corallum consisting of a thin irregular horizontal plate supported 

 on a sub-central peduncle. The upper or calicular surface is undu- 

 lating and has a very thin outer margin. The peduncle is short, 

 irregular in form, and very rugose. Both it and the inferior surface 

 of the expanded part of the corallum have a well-developed epitheca, 

 which is strongly marked with concentric folds or ridges. 



The calices over the peduncle are somewhat hexagonal, but as 

 they approach the outer boundary of the corallum they assume a 

 somewhat rounded, ovoid, or lozenge shape, their greatest diameter 

 being in the direction of their progressive growth, that is, from the 

 centre towards the circumference of the corallum. They are rather 

 superficial, and the intercalicular or mural species consist of thick 

 rounded ridges, constituting the walls. 



The septa are about 33 in number, and form four cycla, of which 

 the fourth is incomplete. Those of the first and second cycla 

 approach nearly to the centre of the visceral cavity and have their 

 inner extremities thickened sufficiently to give something the ap- 

 pearance of a coronet of pali. The septa of the third cycle are 

 about two-thirds of the length of those of the first and second, and 

 those of the fourth are quite short. All of them have a rounded 

 superior margin and a granulated surface, and they are continued 

 over the top of the tumid walls and are continuous with those of 

 contiguous calices. 



Diameter of the calices 1-| to 2 lines. 



The general form of this species is sufficient to distinguish it from 

 all other British species of Isastrcece. The form too of the calices is 

 distinctive, more especially in the worn examples, in which the 

 thick walls are most visible. In these the calices are seen to have 

 but little angularity, but resemble shallow cups having a pretty 

 regularly rounded or ovoid form. 



The species to which it bears the greatest resemblance by the 

 structure of its calices and walls is the Isastrcea foliacea of 

 M. de Fromentel, from which however it is specifically quite distinct. 



Latim^andra Flemingi, Edw. and Haime, Brit. Foss. Cor., pt. ii. 

 p. 136, pi. xxvii. f. 9. 



Examples of this species are not rare at Crickley, and some of them 

 exhibit a peculiarity which is not common in the Oolitic Isastrcece. 



The near connexion of the genus Latimoeandra with the genus 

 Isastroea has been noticed by MM. Edwards and Haime in their 

 History of British Fossil Corals (part ii. p. 137), and again in their 



