R. F. Tomes — British Cretaceous Madrejjoraria. 305 



CcELosMiLiA REGULARis, sp. nov, Plate XIII, Figs, 2, 3, 4. 



The coralluin is siuall, turbinate, straight or a little curved, and 

 attached by a very small foot, and there are distinct but not 

 prominent annular swellings indicating periods of growth. The 

 costas are very indistinct, almost obsolete at the foot, but more 

 defined near the calice. They are sub-equal, and alternately finely 

 granulated and papillated. 



The calice is symmetrical, circular or a little ovoid, and rather 

 deep ; the margin well defined, thin, and prominent, and the fossula 

 small, deep, and a little elongated. 



There are four cycles of septa in six systems ; they are straight in 

 their entire length, regular, not expert, and their margins present a 

 regular curvature from the wall downward into the fossula. Those 

 of the first cycle almost meet in the centre of the visceral cavity, 

 and are undulating in the direction of a horizontal line across them 

 from the wall to the fossula. The undulations form broad, flattened, 

 vertical ridges and furrows on the sides of the septa ; the ridge ou 

 one side corresponding with the furrows on the other. The septa of 

 the second cycle are three-fourtlis the length of the primary ones, 

 and those of the third are a little more than half the length of 

 those of the first cycle, while the septa forming the fourth are short, 

 but vary considerably in different calices. 



in. lines. 



Height of the corallum 10 



Diameter of the calice ... ... ... ... 6.|- 



A larger specimen, showing periods of growth, has a length of 

 1 inch 9 lines, but has a calice of no larger dimensions than that 

 given above. 



The present species may be readily distinguished from all the 

 other British species by the great regularity in the form of the calice, 

 and in the development of tlie septa, as well as by the number of 

 the cycles, and by the length of the septa forming the fourth cycle. 



Hab. — The Upper Chalk of East and West Harnham, Salisbury, 

 and the Upper Chalk of Brighton. 



CcELosMiLiA LA.XA, Edw. & Haime, 

 This was the only British species of the genus accessible to MM. 

 Milne Edwards and Haime when they wrote their history of British 

 fossil corals, and of it they observe, " the septa are very unequally 

 developed, broad, very exsert," and " those of the first and second 

 cycla (sic) united along the lower part of their inner edge." In all the 

 specimens from the Norwich Chalk which I have seen that irregularity 

 is so remarkable that I have wholly failed to define the cycles, and 

 have been obliged to satisfy myself by merely counting the septa. 

 Including those which are merely rudimentary, I find in the largest 

 corallum 68 septa, or four cycles, and 20 septa of the fifth cycle. 

 In another having a calice only a little smaller there are 43 septa 

 only. A third specimen has 44 septa. A fourth specimen, with 

 a calice much reduced in size by recent rejuvenescence, has only 

 32 septa. Other specimens which I have examined have only 



DECADE IV. A'OL. VI. NO. VII. 20 



