CORALS OF THE LONDON CLAY. 15 



and T. Nystiana} to which it is, however, closely allied. The species which it resembles 

 most are, however, Turbinolia Dixonii, T humilis, 2 and T. Bowerbankii. 3 The last of these 

 differs from T. sulcata by its form, which is more elongate and conical, by the thickness 

 of the lower part of its primary costae, and by its very slender columella. Turbinolia 

 Dixonii is easily distinguished by its compressed columella, by the enlargement of its walls 

 near the calice, and by the great prominence of its costae. To conclude this brief com- 

 parison, we must add, that Turbinolia sulcata differs from T humilis by its size, by its 

 form, which is not near so cylindrical as in the latter, and by the normal number of its 

 septa. 



This species is extremely abundant in certain localities of the environs of Paris, such as 

 Grignon, Parnes, and Auvert ; it is also found in the tertiary strata of Hauteville, in 

 Normandy, and in the London Clay at Bracklesham Bay, but it is not common in this last- 

 mentioned deposit. "We are indebted to Mr. Frederick Edwards and to Mr. F. Dixon for 

 the specimens figured in this Monograph. 



2. Turbinolia Dixonii. Tab. Ill, figs. 1, la, lb, 1 c, Id. 



Turbinolia Dixonii, Milne Edwards and J. Haime, Monogr. des Turbinolides, Ann. des 

 Sc. Nat., 3 me serie, vol. ix, p. 238, tab. iv, figs. 2, 2 a, 2 b. 1848. 4 

 — sulcata, Lonsdale, in the MS. -work of M. Dixon on the Chalk Formations and 



Tertiary Deposits of Sussex. 



Corallum slightly contracted just above its basis, and rather inflated near the calice. 

 Costa very thin, and projecting very much, especially towards the lower part of the wall ; 

 those of the third cyclum beginning very near the basis, and those of the first and second 

 cycla beginning almost at the same height. Intercostal furrows nearly of the same size> 

 very broad, and very deep ; intercostal dimples very distinct, separated by small transverse 

 laminae, disposed as usual, in two vertical rows, and prolonged laterally, so as to produce 

 the appearance of transverse fluting on the sides of the costae ; about ten of these dimples 



1 We have given this specific name to the Turbinolia described by M. Nyst, and considered by that 

 author as being referable to the Turbinolia sulcata (see Coquilles et Polyp, des Ter. tert. de la Belgique, 

 p. 629 ; but not the corresponding figure, which is copied from the work of Goldfuss, and belongs to 

 T. sulcata). In order to facilitate the comparison between the British Turbinolia and the species found in 

 other countries, we think it may be useful to point out the characteristic features of the T. Nystiana, which 

 were not known to us when we published our Monograph of Turbinolidae. 



Turbinolia Nystiana, nob. (T. sulcata, Nyst, loc. cit.) Corallum elongated, slightly contracted a little 

 above its basis, and somewhat inflated near the calice. Costae very slightly prominent, and rather thick ; 

 the primary and secondary ones very broad towards the basis; the dimples of the intercostal furrows very 

 small, but distinct, and those of one series alternating with those of the other. No rudiments of a fourth 

 cyclum of costae. Columella small, and almost cylindrical. Septa rather thick, slightly granulated, and 

 forming three complete cycla. Length 3^ lines ; diameter of the calice 1^ line. Fossil from the environs of 

 Brussels. (Cabinet of M. Nyst at Louvain.) 



2 See tab. ii, fig. 4. 3 See tab. ii, fig. 3. 



4 In fig. 2 a of this plate, the principal septa are not broad enough towards the calice, and the 

 concavity of their inner edge is placed rather too high. 



