INTRODUCTION. lxix 



17. Genus Goniophyllum. 



Corallum simple, and affecting the form of a quadrangular pyramid. Calice deep and 

 square. Septa thick and well developed. Tabula central, and but little developed. 



Typ. sp., Goniophyllum pyramidale ; Turbinolia pyramidalis, Hisinger, Lethsea Suecica, tab. xviii, fig. 12. 



18. Genus Chonophyllum. 



Corallum simple, and constituted principally by a series of infundibuliform tabula, super- 

 posed and invaginated, the surface of which presents numerous septal radii equally deve- 

 loped, and extending from the centre to the circumference. No columella nor walls. 



Typ. sp,, Chonophyllum perfoliatum ; Cyathophyllum perfoliatum, Goldfuss, tab. xviii, fig. 5. 



19. Genus Ptychophyllum. 



Strombodes (pars), Lonsdale, Sil. Syst, p. 691, 1839 (not Schweigger.). 



Corallum simple, and organized as in the preceding genus, but having the septal radii 

 strongly twisted towards the centre of the tabulae, so as to constitute a spurious columella. 



Typ. sp., Ptychophyllum Stokesi, nob. ; C. Stokes, Trans, of tbe Geol. Soc, 2d series, vol. i, tab. xxix, 

 fig. 1. ( >T .B. The second figure bearing this number, but not the first.) 



20. Genus Heliophyllum. 



Hall, in Dana, Zooph., p. 396. 1846. 



Corallum simple. Septal apparatus well developed, and producing lateral lamellar 

 prolongations, which extend from the wall towards the centre of the visceral chamber, 

 so as to represent ascending arches and to constitute irregular central tabula, and which 

 are united towards the circumference by means of vertical dissepiments. 



Typ. sp., Heliophyllum Halli, nob. ; Strombodes heliunthoides, Hall, Geol. of New York, No. 48, fig. '.'> 

 (not S. hclianthoides of Phillips). 



21. Genus Metriophyllum. 



Corallum simple, turbinate. Septa well developed, slightly twisted, and extending to 

 the centre of the visceral chamber, through well-developed tabula. 



Typ. sp., Metriophyllum Bouchardi, nob. ; Cyathophyllum mitratum, Michelin, Icon. Zooph., tab. xlvii, 

 fig. 7 (not C. mitratum of Schlotheim). 



