*— striatula, xlvii, 366.f
*— testudinaria, xlvii, 376.f
*Orthoceras multilineatum, xlvii, 369.f
*— primigenium, xlvii, 357.f
*— trentonense, xlvii, 369.
*Orthocerata, in Canada, v, 213f; viii, 84.f
*—, in Indiana, J. T. Plummer, xliv, 295.
*—, divided into three genera, Actinoceras, Ormoceras and Huronia, xxxvii, 233.
*—, structure of, J. Hall, xlvii, 109.
*Orthonota curta, xlviii, 306.f