192 R. F. TOMES ON THE STRATIGRAPHY OE THE 



those of the fifth three fourths the length of the fourth ; and they 

 decrease in regular order, until the ninth cycle has septa which are 

 one fourth the length of the primary ones. 



Height of the corallum | inch. 



Greatest diameter of the calices 1 inch. 



This spe°ies is remarkable for being depressed in form, and at the 

 same time broadly attached. The discoid Montlivaltice are usually 

 either free or attached by a small surface. 



It was found by the Rev. P. B. Brodie, in the Middle Lias at 

 Charmouth, in the bed which has been designated by Mr. Day the 

 Star-fish bed*, and characterized by the presence of OpModenna 

 Egertoni. It has been very kindly lent by him for my use in this 

 paper. 



MoNTLIVALTIA EXCAVATA, n. S. 



Corallum regularly turbinate, broader than high, and attached. 



Epitheca thick, and presenting rounded folds without any trace 

 of costee. 



Calice symmetrically oval, very deep, and the calicular edge very 

 thin. 



Septa projecting to a very trifling extent into the visceral cavity. 

 Their edges are smooth. There are six systems and five cycles. 

 The primary septa pass down the inside of the cavity to near the 

 centre, but do not become more prominent; the secondary ones are 

 half the length of the primary, the tertiary ones two thirds the 

 length of the secondary ; and the fourth and fifth cycles are 

 rudimentary. 



The very regular turbinate and oval form of the corallum, the 

 depth and openness of the calice, and the slight prominence of the 

 septa will at once distinguish this species. 



The five foregoing Middle-Lias species are rather remarkable for 

 their difference from any hitherto recognized Liassic forms. 



I had thought it probable that among the Middle-Lias corals of 

 Normandy there might be some which would exhibit affinities with 

 the species here described ; but I do not find a single nearly affined 

 form among those given by M. de Fromentel in his ' Paleontologie 

 Frangaise.' 



MONTLIVALTIA ? TUBERCULATA, n. S. (PL IX. figS. 7 & 8.) 



In an excavation made through the bottom of the Upper Lias 

 into the marlstone at Adderbury, near Banbury, Mr. Kershaw and 

 I met with two examples of a small sessile coral, which in size and 

 regularity of form much resembles the Trocliocyailius Magnevillianus 

 of the Inferior Oolite of Dorsetshire. 



The wall is thin, and the extreme upper margin free ; the 

 costse rather indistinct, but thick, and corresponding with the septa. 

 The calice is evenly and slightly convex, with a slight central 



* Quart. Journ. Greol. Soc. August 1863 



