Like the order Phacopida, the proetids have exoskeletons that sometime have pits or small tubercles, especially on the glabella ( middle portion of the head ).
32.
The palate ( or hypostome ) is a convex ( the centre bulging down ), subquadrate plate, positioned directly under the frontal part of the glabella.
33.
To the back of the glabella two furrows ( or sometimes one ) cross the glabella forming two rings ( " intercalating ring " and " occipital ring " ).
34.
To the back of the glabella two furrows ( or sometimes one ) cross the glabella forming two rings ( " intercalating ring " and " occipital ring " ).
35.
The size of the glabella and the lateral fringe of the cephalon, together with hypostome variation, have been linked to different lifestyles, diets and specific ecological niches.
36.
Male skulls can have more prominent supraorbital ridges, a more prominent glabella, and more prominent mandibles typically have squarer chins and thicker, rougher muscle attachments than female mandibles.
37.
""'Glabella lucani " "'is a species of sea snail, a marine gastropod mollusk in the family Marginellidae, the margin snails.
38.
""'Glabella reeveana " "'is a species of sea snail, a marine gastropod mollusk in the family Marginellidae, the margin snails.
39.
""'Glabella tyermani " "'is a species of sea snail, a marine gastropod mollusk in the family Marginellidae, the margin snails.
40.
""'Glabella xicoi " "'is a species of sea snail, a marine gastropod mollusk in the family Marginellidae, the margin snails.
