20 BRITISH FOSSIL CORALS. 



Turbinolia minor differs from T. sulcata, T. pharetra, T. Nystiana, T. Dixonii, 

 T. Fredericiana, and T. humilis, by not having the intercostal furrows ornamented with a 

 double row of dimples, a character which in these can always be ascertained with the aid 

 of a good lens. The imperfect development of two of the systems of septa, and the 

 apparent existence of only five systems which is thus produced, is also sufficient to 

 distinguish T. minor from T. costala, T. dispar, T. Prestwichii, and T. Jirma. 



This fossil has been found only in the London Clay, at Alum Bay, in the Isle of 

 Wight. The specimen figured in this Monograph belongs to the cabinet of Mr. J. S. 

 Bowerbank. 



7. Turbinolia firm a. Tab. II, figs. 4, 4 a, 4 b. 



Corallum subturbinate, and elongated ; narrow at the basis. Costa thick, obtuse, 

 closely set, and prominent ; those of the first two cycla very broad below the under end of 

 the tertiary ones. Intercostal furrows narrow, and presenting neither mural dimples nor 

 well-marked lateral transverse flutings or costal crenations. Columella compressed, and not 

 very large. Septa rather thin, delicately granulated, and forming three complete cycla ; 

 the tertiary ones less developed than the secondary ones, and cemented to the primary 

 ones at a small distance from the columella. Height three lines and a half; diameter of 

 the calice, one line and a half. 



Turbinolia Jirma differs from T. costata, T. dispar, T. Bowerbankii, and T. Fredericiana, 

 by the non-existence of a fourth cyclum of more or less developed costae ; from T. minor 

 and T. humilis, by the complete development of the tertiary septa in the six systems, and 

 from T. sulcata, T. pharetra, T. Nystiana, T. Bixonii, and T. humilis, by the non-existence 

 of dimples in the intercostal furrows. It resembles very much T. Prestwichii, but differs 

 from it by its general form and by its thick obtuse costse. 



We have as yet seen but one specimen of this species ; it was found at Barton, and 

 given to us by Mr. Dixon : unluckily the artist in whose hands it was placed in order to 

 have it figured, has broken it so much that it is no longer recognisable. 



8. Turbinolia Prestwichii. Tab. Ill, figs. 5, 5 a, 5 b. 



Corallum of a cylindroid form, much elongated, and very obtuse at the basis. Costa 

 strong, rather thick, and very prominent, especially towards the basis ; those of the third 

 cyclum beginning much lower down than in most species (.figs. 5 a), and contributing to form 

 the convex star seen at the basis of the corallum (fig. 5 b). Some slight vestiges of a fourth 

 cyclum of costse at the bottom of the intercostal furrows near the calice. These furrows 

 very deep, becoming very narrow near the wall, and not presenting any mural dimples 



