Taken from the Anomia, and with great propriety, as its characteristic
differences are very great; the perforation of the Anomia is always in
the smaller valve, which is attached to the larger by a cardinal
ligament, while in the Terebratula the perforation is always in the
larger valve, which is connected to the smaller by teeth at the hinge.
In some the valves are smooth, and in others grooved longitudinally.
Shell thin, equilateral, sub-triangular, inequivalve; one of the valves
larger and more convex than the other, prolonged behind by a sort of
heel, sometimes recurved, and pierced by a round hole at its extremity;
frequently sloped more or less by a cleft of variable form; the opposite
valve smaller, more flat, sometimes formed like a lid, having in the
interior a system of support variable in form and complication in every
true species; hinge limited, prominent, and formed by two articulating
surfaces of one valve placed between corresponding projections of the
other; a kind of tendinous ligament issuing from the sloping cleft of
the shell, by which it is attached to marine bodies.
Terebratula vitrea.
T. dilatata.
T. rotunda.
T. flavescens.
T. dentata.
T. dorsata.
T. pisum.
T. globosa.
T. sanguinea.
T. caput-serpentis.
T. truncata.
T. psittacea.
_T. dorsalis._ The dorsal Terebratula. Pl. 17, fig. 1.
The summit of the large valve pierced with a round hole, very
circumscribed; grooved longitudinally; valves as if cut sloping in the
middle line.
_T. globosa._ The globose Terebratula.
Species smooth, with the valves rounded at their anterior edge.
_T. caput serpentis._ The Serpent’s-head Terebratula.
Species grooved, with the summit or heel of the large valve deeply
hollowed even to the edge of the articulation; the slope rounded; the
valves sub-bilobate by the apparent slope of the anterior edge.