Later on he was engaged for about three years at Dolgelly, another though small gold-mining region, and here he carefully investigated the rocks and fossils of the Lingula Flags, his observations being published in an important and now classic memoir in the " Geological Magazine " for 1867.
22.
The common fossils include plants ( Actinophyllum, Chondrites ), ostracods, phyllocarids, eurypterids, trilobites ( less common than in the older groups ), numerous brachiopods ( " Lingula minima ", " Chonetes striatella " ), gasteropods, pelecypods and cephalopods ( " Orthoceras bullatum " ).
23.
The margin of this opening is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula mandibulae, which gives attachment to the sphenomandibular ligament; at its lower and back part is a notch from which the mylohyoid groove runs obliquely downward and forward, and lodges the mylohyoid vessels and nerve.
24.
In the oldest tertiary beds a few living shells may still be found in the midst of a multitude of extinct forms . . . The Silurian " Lingula " differs but little from the living species of this genus " . " Lingula " is among the few brachiopods surviving today but also known from fossils over 500 million years old.
25.
In the oldest tertiary beds a few living shells may still be found in the midst of a multitude of extinct forms . . . The Silurian " Lingula " differs but little from the living species of this genus " . " Lingula " is among the few brachiopods surviving today but also known from fossils over 500 million years old.
