Late Cambrian – Early Silurian
Cyrtolitidae is an extinct family of slow-moving low-level epifaunal grazers
Description of the Family
- Anal emargination a shallow sinus
- Commonly angular but without slit or selenizone
- Generally open coiling especially in adult whorls
Treatise on Invertebrate Paleontology, Part I, Vol. 1 (1960):
- Anal emargination a shallow sinus, commonly angular but without slit or selenizone; coiling generally open, especially in adult whorls.
Ulrich & Scofield (1897):
- Symmetrical involute shells; volutions two or three, barely in contact, sharply angular dorsally; aperture not expanded, the sinus V-shaped, never deep, sometimes wanting; no slit, and the bands occurs only in Cyrtolitina; surface reticulate.