168 E. E. TOMES ON THE GEEAT-OOLITE MADEEPOEAEI1. 



12. On the Fossil Madeepoeaeia of the Geeat Oolite of the Counties 

 of Gloucestee and Oxfoed. By Eobeet E. Tomes, Esq., E.G.S. 

 (Bead January 24, 1883.) 



(Plate VII.) 



Inteodtjction. — I have already in two communications brought 

 before the notice of this Society some new or imperfectly under- 

 stood Madreporaria from the Lias and Inferior Oolite, and have at 

 the same time made additions to our knowledge of their strati- 

 graphical distribution as well as to the localities where they have 

 been met with*. 



In the present communication I propose to continue the series of 

 papers on the same subject, in ascending order, and furnish some 

 particulars not before noted respecting the Madreporaria of the 

 Great Oolite of the counties of Gloucester and Oxford. 



The following genera now appear as new to the Oolite of this 

 country. Bathycoenia is a new genus, and contains two species, 

 which appertain to the family Astrceidse and the subfamily Eusmi- 

 linae. Favia, Astroccenia, JEnalloJielia, and Tricycloseris are ge- 

 nera already established, the appearance of which in the Oolite of 

 this country is now for the first time recorded. Two other genera 

 already made known by me as occurring in the Inferior Oolite are 

 here added to the list of genera of the Great Oolite. They are 

 Gonfusastrma, which is represented by two species, and Oroseris, 

 which contains only one. 



In my paper on the Madreporaria of the Inferior Oolite of the 

 neighbourhood of Cheltenham, read before the Society in May last 

 yearf, I found it necessary to make some reforms in the nomen- 

 clature of certain species. This resulted from a more extended 

 investigation into their mode of growth and increase ; and it was 

 seen that the two very dissimilar processes, fissiparity and gemmation, 

 had been sometimes confounded. Thus the usually accurate obser- 

 vation of MM. Edwards and Haime failed, in the so-called Theco- 

 smilia gregaria, to distinguish between them; and the error of 

 supposing that the species increased by division was continued by 

 Prof. Duncan and myself. A few additional remarks will not be 

 undesirable at the present moment. 



M. de Eromentel, who calls especial attention to the necessity of 

 distinguishing between fissiparity and gemmation, observes that the 

 latter process produces corallites which have a new and distinct 

 wall, whereas the corallite which is the result of fissiparity is not 

 similarly enclosed, even when it has become separated from the 

 parent calice. My own investigations have led me to a somewhat 

 modified conclusion ; for I believe that when gemmation takes place 

 in species having serial calices, the young corallite is not similarly 



* Quart. Journ. GTeol. Soc. vol. xxxiv. p. 179, and vol. xxxviii. p. 409. 

 t Quart. Journ. Geol. Soc. vol. xxxviii. p. 429. 



