ClipArt ETC
This is a diagram showing the rocks of the successive periods of time. They are shown in order from the Archaean, in Northern New York, southwestward to the Coal-formation of Pennsylvania, showing that they succee one another on the map simply because they come to the surface in succession

Archaean Time

This is a diagram showing the rocks of the successive periods of time. They are shown in order from…

"Upper aspect of the primordial cranium, with the membrane-bones removed. An, angular; ao, anteorbital; Ar, articulary; B, basal; D, dentary; E, ethmoid; F, frontal; Ma, mastoid; Mp, metapterygold; Mx, maxillary; N, nasal; O, operculum; Oc, occipital; Pa, parietal; Pl, palatine; Pmx, premaxillary; po, postorbital; Prf, prefrontal; Pt, post-temporals; Ptf, postfrontal; Ptr, pterygold; Q, quadrate; S, suspensorium; So, suboperculum; Sp, sphenold; Spl, splenial; St, supratemporals; T, tympanic lamina; Tu, turbinal; v, vomer; x x, small ossicles; x' x', spiraculars." — Encyclopedia Britannica, 1893

Polypterus Skull

"Upper aspect of the primordial cranium, with the membrane-bones removed. An, angular; ao, anteorbital;…

"Lower aspect of the primordial cranium, with the membrane-bones removed. An, angular; ao, anteorbital; Ar, articulary; B, basal; D, dentary; E, ethmoid; F, frontal; Ma, mastoid; Mp, metapterygold; Mx, maxillary; N, nasal; O, operculum; Oc, occipital; Pa, parietal; Pl, palatine; Pmx, premaxillary; po, postorbital; Prf, prefrontal; Pt, post-temporals; Ptf, postfrontal; Ptr, pterygold; Q, quadrate; S, suspensorium; So, suboperculum; Sp, sphenold; Spl, splenial; St, supratemporals; T, tympanic lamina; Tu, turbinal; v, vomer; x x, small ossicles; x' x', spiraculars." — Encyclopedia Britannica, 1893

Polypterus Skull

"Lower aspect of the primordial cranium, with the membrane-bones removed. An, angular; ao, anteorbital;…

"Side view, with the membrane-bones. An, angular; ao, anteorbital; Ar, articulary; B, basal; D, dentary; E, ethmoid; F, frontal; Ma, mastoid; Mp, metapterygold; Mx, maxillary; N, nasal; O, operculum; Oc, occipital; Pa, parietal; Pl, palatine; Pmx, premaxillary; po, postorbital; Prf, prefrontal; Pt, post-temporals; Ptf, postfrontal; Ptr, pterygold; Q, quadrate; S, suspensorium; So, suboperculum; Sp, sphenold; Spl, splenial; St, supratemporals; T, tympanic lamina; Tu, turbinal; v, vomer; x x, small ossicles; x' x', spiraculars." — Encyclopedia Britannica, 1893

Polypterus Skull

"Side view, with the membrane-bones. An, angular; ao, anteorbital; Ar, articulary; B, basal; D, dentary;…

"Lower aspect of the skull, part of the bones being removed on the side. An, angular; ao, anteorbital; Ar, articulary; B, basal; D, dentary; E, ethmoid; F, frontal; Ma, mastoid; Mp, metapterygold; Mx, maxillary; N, nasal; O, operculum; Oc, occipital; Pa, parietal; Pl, palatine; Pmx, premaxillary; po, postorbital; Prf, prefrontal; Pt, post-temporals; Ptf, postfrontal; Ptr, pterygold; Q, quadrate; S, suspensorium; So, suboperculum; Sp, sphenold; Spl, splenial; St, supratemporals; T, tympanic lamina; Tu, turbinal; v, vomer; x x, small ossicles; x' x', spiraculars." — Encyclopedia Britannica, 1893

Polypterus Skull

"Lower aspect of the skull, part of the bones being removed on the side. An, angular; ao, anteorbital;…