xvi BRITISH FOSSIL CORALS. 



15. Genus Placocyatiius. 



Milne Edw. and J. Haime, loc. cit., p. 327, 1848. 



Corallum simple, pedicellate, and slightly compressed. Columella lamellar, with its 

 apical margin straight. Pali thin, resembling lobes of the septa, and corresponding only to 

 the septa of the penultimate and antipenultimate cycla; those facing the latter more 

 developed than the others (a disposition which forms an exception to the common rule). 

 Septa numerous, thin, broad, and slightly exsert. Costa distinct from the top to the 

 bottom of the walls, but projecting very little, nearly equal, and appearing to bifurcate 

 towards the upper part of the corallum. 



Typ. sp., Placocyathus apertus, Milne Edw. and J. Haime, loc. cit., tab. x, fig. 10. 



Second Tribe— TURBINOLINiE. 

 Milne Edw. and J. Haime, loc. cit., p. 235, 1848. 



Corallum destitute of pali ; the septa extending to the columella, or meeting in the 

 centre of the visceral chamber. 



§ 1. Wall naked, or having only an incomplete epitheca. 

 16. Genus Turbinolia. 



Turbinolia (in parte), Lamarck, An. sans Vert., vol. ii, p. 359, 1816 ; Turbinolia (in parte), Ehrenberg, 

 op. cit., p. 53, 1834 ; Dana, op. cit., p. 374 ; Turbinolia, Milne Edw. and J. Haime, loc. cit., p. 235, 1848. 



Corallum simple, conical, straight, and presenting no trace of adherence. Calice circular. 

 Columella styliform. Septa exsert, those of the last cyclum bent toward the neighbouring 

 ones and united to them. Costa lamellar, straight, entire, and very projecting ; the inter- 

 costal grooves presenting a double series of small dimples, resembling pores. 



Typ. sp., Turbinolia sulcata, Lamarck, Hist. Anim. sans Vert., vol. ii, p. 231 ; Cuvier and Brongniart, 

 Geographie Mineral, des Envir. de Paris, tab. ii, fig. 3. 



17. Genus Sphenotrochus. 

 Milne Edw. and J. Haime, loc. cit., p. 240, 1848. 



Corallum simple, presenting no trace of adherence, straight, and cuneiform. Calice 

 elliptical. Columella lamellar, and occupying the great axis of the calice ; its upper margin 

 flexuous and bilobate. Septa broad, slightly exsert, and forming three cycla ; apparently 

 twelve systems in the adult. Costa broad, not very prominent, in general crispate, or 

 represented by series of papillous tubercles. 



Typ. sp., Sphenotrochus crispus, Milne Edw. and J. Haime, loc. cit., p. 241 ; Turbinolia crispa, Lamarck, 

 op. cit., vol. ii, p. 231 ; Milne Edwards, Atlas du Regne Animal de Cuvier, Zoopb., pi. lxxxii, fig. 4. 



