JR. F. Tomes — Inferior Oolite Madreporaria. 391 



species, the corallites of which are placed close to each other. Many 

 well-preserved calices have now been examined, and the generic 

 characteristics fully made out. Prof. Duncan assumes that the simple 

 corallum of Axosmilia Wrighti has been taken by me as the foot- 

 stalk of Donacosmilia, but I never for a moment entertained such a 

 supposition. On the contrary, I distinctly stated my belief that 

 both Axosmilia Wrighti and Montlivaltia Rolli were nothing more 

 than single corallites of Donacosmilia broken off at their point of 

 attachment to the parent stem, and I have seen nothing to induce 

 me to modify that conclusion. The entire margins of the septa, 

 which are so peculiarly characteristic and common to ell the above- 

 mentioned forms, are not so much as alluded to by Prof. Duncan 

 in his late paper. 



Placophyllia gracilis, sp. nov. (Plate X. Figs. 5 and 6.) 



Single corallites of a Coral having a gracile growth, and almost 

 always in an indifferent state of preservation, have frequently been 

 found in the Lower Coral-bed of the Cotteswolds. These could not 

 be attributed to any known species, and were too fragmentary for 

 description. Eenewed search at those places where that Coral-bed is 

 exposed has brought to light some better-preserved specimens, which 

 may be described as follows : — 



The corallum consists of a bush-shaped mass of rather closely 

 placed and nearly parallel corallites, which have nearly the same 

 diameter from the bottom to the top. Lateral gemmation takes places 

 at considerable intervals, and the young corallites thus produced 

 spring from the parent-stem horizontally, but speedily assume a 

 perpendicular position by the side of the older corallite, and both 

 grow upwards together. All the corallites, old and young, have a 

 well-developed epitheca, which presents numerous and regular rings 

 of growth. The walls are produced upwards, and with their epithecal 

 covering, form thin and prominent margins to the calices. 



The calices are ovoid and deep, and the fossula is elongated. The 

 margins of the septa have very little curvature, but slope inward 

 and downward in nearly a straight line. At the wall the septa are 

 thick, but they diminish in thickness, and become quite thin as they 

 approach the columella ; though there is sometimes a little thinning 

 just at their union with it. They are twenty -four in number, that 

 is to say, three cycles in six systems. The first and second cycles 

 are united to the columella, and two of the primary ones run into 

 its two ends, and with it divide the calice longitudinally in half. 

 The septa of the third cycle are three-fourths the length of the 

 primary and secondary ones. There are a few rudimentary septa 

 of the fourth cycle in some of the systems. The columella is thin, 

 well defined, but not prominent, and is about one-third the entire 

 length of the calice. 



Diameter of the corallites from two to three lines. Their height 

 cannot be ascertained. 



This species bears considerable resemblance to the PlacopliyUia 

 rugosa of Becker, from the Corallien of Nattheim. 



