INTRODUCTION. XV 
18. Genus PLatyTRocHus. 
Milne Edw. and J. Haime, loc. cit., p. 246, 1848. 
Corallum simple, straight, cuneiform, and presenting no trace of adherence. Cualice 
elliptical.  Codumella fasciculate, and terminated by papilla. Septa exsert, very broad, 
nearly equal, and very strongly granulated ; three cycla; systems equally developed. Coste 
of two sorts, those that occupy the middle of each side of the corallum enlarging as they 
ascend ; the lateral ones larger and much broader at their bases than near the calice, so as 
to render the lateral edges of the corallum almost parallel. 
Typ. sp., Platytrochus Stokesii, Milne Edw. and J. Haime, loc. cit. tab. vii, fig. 7; Turbinolia Stokesii, 
Lea, Contrib. to Geol., tab. vi, fig. 207. 
19. Genus CERATOTROCHUS. 
Milne Edw. and J. Haime, loc. cit., p. 248, 1848. 
Corallum simple, subpedicellate, free in the adult state, and recurved towards its basis. 
Calice circular, or nearly so. Columella fasciculate, and highly developed. Septa straight, 
broad, and exsert. Coste partly armed with spmes, crests, or small lobular processes. 
Typ. sp., Ceratotrochus multiserialis, Milne Edw. and J. Haime, loc. cit., tab. vii, fig. 5; Turbinolia 
multiserialis, Michelotti, Spec. Zool. tab. ui, fig. 7. 
20. Genus DiscoTrocuus. 
Milne Edw. and J. Haime, loc. cit., p. 251, 1848. 
Corallum simple, discoidal, and presenting no trace of adherence. Ca/ice circular, and 
almost flat. Colwmella fasciculate, and terminated by papillae equal in size. Septa straight, 
very broad, and projecting but little laterally. Wad/ horizontal. Coste straight and simple. 
Typ. sp., Discotrochus Orbignyanus, Milne Edw. and J. Haime, loc, cit., tab. vii, fig. 6. 
21. Genus DESMOPHYLLUM. 
Ehrenberg, op. cit., p. 75, 1834. 
Corallum simple, and adherent by a broad basis. Calice with a very deep fossula. No 
columella (a character which distinguishes this group from all the preceding 'Turbinoline). 
Septa broad, very exsert, free almost all along their inner edge, and grouped in fasciculze ; 
those of the last cyclum taller than those of the penultimate cyclum, and cemented 
exteriorly to the older septa. Coste distinct near the calice, but obsolete on the lower part 
of the wall, where there are only a few granulations. 
Typ. sp., Desmophyllum crista-galli, Milne Edw. and J. Haime, loc. cit., tab. vii, fig. 10. 
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