INTRODUCTION. Ixix 
17. Genus GoNIOPHYLLUM. 
Corallum simple, and affecting the form of a quadrangular pyramid. Calice deep and 
square. Sepéa thick and well developed. Zadule central, and but little developed. 
Typ. sp., Gonrophyllum pyramidale ; Turbinolia pyramidalis, Hisinger, Letheea Suecica, tab. xviii, fig. 12. 
18. Genus CHONOPHYLLUM. 
Corallum simple, and constituted principally by a series of infundibuliform ¢adule, 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 PrycHorpHYLLUM. 
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 tabulee, so as to constitute a spurious colwmella. 
Typ. sp., Ptychophyllum Stokesi, nob.; C. Stokes, Trans. of the Geol. Soc., 2d series, vol. i, tab. xxix, 
fig. 1. (N.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 ¢adu/@, and which 
are united towards the circumference by means of vertical dissepiments. 
Typ. sp., Heliophyllum Halli, nob.; Strombodes helianthoides, Hall, Geol. of New York, No. 48, fig. 3 
(not S, helianthoides of Phillips). 
21. Genus MEtTRIoPHYLLUM. 
Corallum simple, turbinate. Sepfa 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). 
