46 BRITISH FOSSIL CORALS. 



not be unworthy of notice that these five species are as yet the only representations of the 

 genus Cyathina that have been met with in the Chalk Formation. At first sight they appear 

 very similar, but by an attentive examination, constant and well-defined characteristic 

 differences are found between all. In C. Koninckii, the corallum is always shorter, and 

 more regularly turbinate ; the pali are thicker, and the columella is reduced to two or three 

 thick, twisted processes. In C. Bower bankii, on the contrary, the pali are much thinner, 

 and the surface of the walls appears granulous. C. cylindrica and C. Breda differ from 

 it by a very peculiar character, which exists also in C. Koninckii, but which is not met with 

 in any other species of the same genus, and is indeed quite an exception to the family of 

 Turbinolidae, the pali being only six in number, although the four cycla of septa be com- 

 plete, and corresponding to the septa of the antepenultimate cyclum, whereas they usually 

 correspond to those of the penultimate cyclum. The thin, elongate form of C. Breda and 

 the quite cylindrical form of C. cylindrica, will also help to distinguish them from C. laevigata, 

 which differs also from C. Bebeyana, by the latter having a well-marked epithecal fold near 

 the calice, a small columella, and thinner pali. 



Cyathina laevigata is found in the Upper Chalk at Dinton, in Wiltshire ; specimens may 

 be seen in the collections of the Geological Society, of Mr. Bowerbank, and of the Museum 

 at Paris. 



set, and having stronger lateral granulations near the inner edge. The primary ones larger and rather 

 thicker than the others, but differing very little from the secondary ones ; the tertiary ones are thinner and 

 smaller ; those of the fourth cyclum are distinct, but very small. Pali prominent, extremely thick, narrow, 

 strongly granulated laterally, and corresponding to the secondary septa. Height of the corallum about six 

 lines ; diameter of the calice three lines. Fossil from the Chalk of St. Peter's Mountain, at Maestricht ; speci- 

 mens exist in the Museum of Natural History of Paris, and in the Tylerian Museum at Haarlem. 



Cyathina Bred^e, nobis. This fossil corallum, which we dedicate to Professor Van Breda, is adherent 

 by a rather broad basis, contracted immediately above, elongate, slender, much bent, and cylindrical towards 

 its upper part. The costse are not well marked, and the walls are almost smooth, but present sometimes 

 slight horizontal folds. Calice circular; fossula shallow. Columella but little developed, and sometimes 

 reduced to a single twisted process. Septa forming four complete cycla ; but those of the last cyclum 

 rudimentary though distinct ; the primary ones rather thick, especially towards the inner edge ; the 

 secondary ones resembling those of the first cyclum, but rather narrower ; the others very thin. The 

 granulations on the sides of the septa are conical, and very prominent. The pali corresponding to the 

 secondary septa, well developed, prominent, narrow, and appearing very thick, because they are flexuous. 

 Height, seven or eight lines ; diameter of the calice, two lines and a half. This species is also found in the 

 fossil state in the Chalk of St. Peter's Mountain, at Maestricht; specimens exist in the collections of MM. 

 Van Riemsdyck and Bosquet, at Maestricht ; of M. Van Breda, at Haarlem ; and of the Museum at Paris. 



Cyathina Debeyana nob. Corallum cylindrical, elongate, slightly curved, and presenting near the 

 calicular margin a small but well-marked circular band, representing an incomplete epitheca. Calice 

 circular; fossula not deep. Septa unequal, closely set, somewhat exsert, rather thick externally, but thin 

 towards the inner edge, and forming four complete cycla; the secondary ones almost as large as those of 

 the first cyclum. Pali rather narrow, and not very thick. Height, one inch ; diameter of the calice, three 

 lines ; depth of the fossula, one line. Fossil from the Chalk of Aix-la-Chapelle, discovered by M. Debay. 



