CORALS OF THE UPPER CHALK. 45 



towards the basis, but presenting towards the calice slightly-marked costee, which are 

 closely set, glabrous, or very delicately granulated, and almost equal in size. Calice 

 circular, or sometimes rather oval, shallow. Columella moderately developed, not projecting 

 in the centre of the calicalar fossula, composed of six or eight twisted, vertical processes, 

 and terminated by an equal number of papillae. Septa forming four cycla, the last of 

 which is in general incomplete ; the septa of the fourth and fifth orders not existing in one 

 half of three of the systems or even of all six of these, so that the number of these 

 radiate laminae is reduced to 42, or even to 36-; sometimes, however, four of the systems 

 are complete, and the number of the septa then amounts to 48. These septa are well 

 developed, closely set, thin, but slightly granulated, rather exsert, and almost equal ; the 

 principal ones are, however, a little thicker than the others. The pali are narrow, but 

 very thick, prominent, aud terminated by a curved edge ; they all correspond to the 

 tertiary septa, and in the specimens where the fourth cyclum is complete, they exist in 

 front of all the septa of the penultimate cyclum, and are therefore twelve in number ; but 

 they are never so numerous when the fourth cyclum remains incomplete, and never 

 correspond to tertiary septa that are not separated by septa of the fourth cyclum. As 

 mentioned above, these latter septa are often wanting in one half of three of the systems, 

 and in that case there are consequently no pali corresponding to the tertiary septa of these 

 incomplete half systems,, so that the number of pah is reduced to nine ; two belonging to 

 each of the three complete systems, and one to each of the incomplete ones. The same 

 rule also holds good when all the six systems are deficient of the septa of the fourth 

 cyclum in one of their halves ; the tertiary septa of the complete halves are the only ones 

 having corresponding pah, so that the number of these organs is only six. The height of 

 the corallum varies between one inch and one inch and a half; in the tall specimens the 

 diameter of the calice is about four lines ; in the short and broad ones it is sometimes five lines. 



This species is easily distinguished from the Cyathina Cyat/ius, 1 C. Smitldi? and 

 C. pseudoturbmolia, 2, by its never having a fifth cyclum of septa. C. Guadulpensis* and 

 C. arcuatd* differ from the above-described fossil by the existence of distinct costae down 

 to the basis of the walls, and by the large size of the pali. C. laevigata most resembles 

 C. Koninckii, 6 C. Boioerbanlriii C. Debeyana, C. Breda, and C. cylindrical and it may 



1 See our Monograph of Turbinolidae, Ann. des Sc. Nat., 3 me s£rie, vol. ix, p. 287, tab. iv, fig. 1. 



2 Loc. cit., p. 288. 3 Loc. cit., p. 289, tab. ix, fig. 1. * Loc. cit., p. 290. 

 5 Loc. cit., p. 290. c Loc. cit., p. 290. 7 Loc. cit., p. 292. 



8 The three last-mentioned species were not known to us when we published our Monograph of 

 Turbinolidae, and in order to render the comparison between the T. lavigata and the rest of the genus more 

 complete, it appears to us advisable to give a description of them here. 



Cyathina cylindrica, nob. Corallum fixed by abroad basis, regularly cylindrical, straight, and not 

 very tall. Costae equal, flat, straight, closely set, not very broad, and very indistinct, especially towards 

 the basis. Calice circular, having a thick edge, and the fossula rather shallow. Columella very small, and 

 reduced to two or three small, almost indistinct, tubercles. Septa forming four complete cycla, very closely 



