Xvi BRITISH FOSSIL CORALS. 
15. Genus PLACOCYATHUS. 
Milne Edw. and J. Haime, loc. cit., p. 327, 1848. 
Corallum simple, pedicellate, and slightly compressed. Colwmella \amellar, with its 
apical margin straight. Pa/i 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. Coste 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—TURBINOLIN J. 
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. 538, 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. Ca/ice circular. 
Columella styliform. Septa exsert, those of the last cyclum bent toward the neighbouring 
ones and united to them. Cosf@ lamellar, straight, entire, and very projecting ; the inter- 
costal grooves presenting a double series of small dimples, resembling pores. 
Typ. sp., Turbinolia suleata, Lamarck, Hist. Anim. sans Vert., vol. ii, p. 231; Cuvier and Brongniart, 
Géographie 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. Colwmella lamellar, and occupying the great axis of the calice; its upper margin 
flexuous and bilobate. Seta broad, slightly exsert, and forming three cycla; apparently 
twelve systems in the adult. Coste 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 Régne Animal de Cuvier, Zooph., pl. Ixxxii, fig. 4. 
