182 E. p. TOMES ON MADEEPOEAEIA 



continuous, nearly conceal the wall, much as in unworn calices of 

 Gonvexastrcea. Those of the first cycle extend towards the centre 

 of the calice, and have a slight swelling at their inner end. The 

 septa of the second cycle are half the length of those of the first, 

 while those of the third are half the length of the second. 



The lamellar columella has very little prominence, and is so placed 

 between two opposite septa of the first cycle as to fill up the space 

 between them so closely that, when the calices are worn down, the 

 whole becomes a continuous and straight line across the calice, 

 dividing it in half. Both septa and septal costse have their margins 

 distinctly crenulated, the crenulations being small, pointed, and 

 irregular. Their sides also are furnished with coarse irregular 

 granulations, which are also observable in the spaces between them. 



Height of the corallum 1 inch 6 lines ; the diameter is about the 

 same, and the calices are about 1 line in diameter. The spaces between 

 the calices considerably exceed the diameter of the latter, excepting 

 in one or two crowded spots. 



Excepting the single example from Farley Down, I have not 

 examined a species representing this genus. 



Genus Convex aste^a, d'Orb. 



As Conveocastrcea Waltoni, our only representative of the genus, 

 was described from specimens collected by the late Mr. Walton at 

 the Hampton Kocks near Bath, it is, perhaps, desirable that I should 

 state that I have compared specimens from that locality with others 

 from the coralline deposits in the Great Oolite of Oxfordshire, and 

 find them to be in all respects similar. 



The differences between Conveocastrcea and Cryptocoenia have been 

 recently defined with great clearness by M. Koby in his work on the 

 ' Jurassic Corals of Switzerland,' now in course of publication. He 

 observes that the former differs from the latter in having the septal 

 costse less numerous, rarely confluent, and not completely concealing 

 the intercalicular spaces. 



Genus Montlivaltia, Lamx. 



I have often met, in the Great Oolite, with a supposed Montlivaltia 

 which is characterized by a stunted form, a naked costulated wall, 

 and rather a small number of very thin septa. The fossula is elon- 

 gated, much as in Montlivaltia caryophytlata. The mural costae are 

 rather far apart, and have a prominence according to the order of 

 the septa they represent. They are wholly without tubercles or 

 papillae, and if their smooth and rounded form may be taken as any 

 indication of the nature of the margins of the septa, the latter may 

 also have been smooth. In that case it could not be placed in the 

 genus Montlivaltia. It occurs in the Great Oolite of the Eollright 

 and Stonesfield railway-cuttings, in the Caps-Lodge and Milton 

 quarries, and I have a specimen taken from the coral-bed on Combe 

 Down. From none of these places have I obtained well-preserved 

 specimens. 



