HELICOSTEGINA R. W. Barker and Grimsdale. 1936

 

 

Type species: Helicostegina dimorpha R. W. Barker and Grimsdale, 1936; OD.Helicostegina R. W. Barker and Grimsdale. 1936(^*138), p. 233.HelicolepidinoidesTan, 1936 (*3117), p. 992: type spe­cies: Helicostegina gyralis R. W. Barker and Grimsdale. 19361*1381, p. 236; OD.Test lenticular, early chambers in an involute trochospiral coil, later ones subdivided ventrally to form small chamberlets in early species or subdivided on both sides in later species, adult test with peripheral flange and arcuate chambers in annular series around the periphery of the juvenile stage; wall sur­face pustulose to papillose; aperture a nar­row slit near the inner margin of the final chamber. M. to U. Eocene; Trinidad; Mexico.