|Apical cycle||upper part of sphenolith, formed of most steeply inclined cycle of elements. Types:
Monocrystalline formed of one crystal-unit; e.g. S. heteromorphosus, S. belemnos.
Duocrystalline formed of two crystal-units; e.g. S. distentus, S. furcatulithoides.
Compound formed of several crystal-units; e.g. S. radians, S. abies.
|Apical spine||elongate extension of apical cycle.|
|Base||all of sphenolith except the apical spine.|
|Blade||one of three sub-parts of an element, only seen in well preserved material.|
|Core||centre of radiation of elements.|
|Element||basic component of sphenoliths, each element appears to be a single crystal-unit.|
|Lateral cycles||cycles between apical and proximal cycles, not always present.|
|Proximal cycle||lowermost cycle of elements.|
|Upper/lower part||part above/below the core.|