INTRODUCTION. xvii 



18. Genus Platytrochus. 

 Milne Edw. and J. Haime, loc. cit., p. 246, 1848. 



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

 elhptical. Columella fasciculate, and terminated by papillae. Septa exsert, very broad, 

 nearly equal, and very strongly granulated; three cycla; systems equally developed. Costa 

 of two sorts, those that occupy the middle of each side of the coraEum 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. Costa partly armed with spines, crests, or small lobular processes. 



Typ. sp., Ceratotrochus multiserialis, Milne Edw. and J. Haime, loc. cit., tab. vii, fig. 5 ; Turbinolia 

 multisenalis, Michelotti, Spec. Zool. tab. ii, fig. 7. 



20. Genus Discotrochus. 



Milne Edw. and J. Haime, loc. cit., p. 251, 1848. 



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

 almost flat. Columella fasciculate, and terminated by papillae equal in size. Septa straight, 

 very broad, and projecting but little laterally. Wall horizontal. Costa 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 Turbinohnae) . 

 Septa broad, very exsert, free almost all along their inner edge, and grouped in fasciculae ; 

 those of the last cyclum taller than those of the penultimate cyclum, and cemented 

 exteriorly to the older septa. Costa 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. 



