BIVALVIA. 28] 
Panopna.* AMenard de la Groye, 1807. 
Mya (sp.) Linn. Broc. Panopra. Swains. 1840. 
CuHaM®PHOLAS (sp.) Petiver. Panopoga. Nyst, 1844. 
Giycimeris. Lamk. 1812. Homomya (sp.) Agass. 1845. 
Panopma. Goldf. Phil. Bronn. Valenciennes. 
Generic Character, Shell transversely oblong, equivalved, inequilateral, more or 
less gaping at both extremities; surface smooth or marked by rough and somewhat ir- 
regular lines of growth ; elongated impressions by the adductors ; mantle-mark with a 
large, deep sinus; hinge furnished with one conical tooth in each valve; ligament 
external, placed on a prominent fulcrum. 
Animal with very long and extensible siphonal tubes united to their extremities ; 
mantle closed throughout its length, except a small opening in front for the passage 
of a short, stout, muscular foot; large and strong adductor muscles. 
This genus is closely related to J/yqa, in the animal as well as in the shell, differing 
principally by the position of the hinge-ligament, which in this is placed upon a 
prominent ridge, and its action consequently different. The animal has very long 
siphonal tubes, which are incapable of being withdrawn into the shell, and are con- 
sequently thickened, and covered with a strong coriaceous epidermis. 
In 1839, M. Valenciennes published a valuable monograph of this genus, and 
described the animal of one species found on the shore of Port Natal, which 
seems to have been an inhabitant of shallow water, and left dry at the retreat 
of the tide. Its tubes were observed protruding through the sand, and when 
alarmed retreated backward by means of its powerful foot to the depth of several 
feet. 
Some of the Oolitic Fossils belong to this genus. 
Dr. Gray considers the name of G/ycimeris, proposed by Klein, 1753, as entitled to 
be used for this genus, but the date is anterior to our starting point, viz. the 12th 
ed. Linn., 1767. 
1. Panopea Norvecica, Spengler. Tab. XXIX, fig. 1, a—e. 
Mya Norvecica. Speng. Skrivt. Natu. Silskal, vol. iii, part 1, p. 46, pl. 2, fig. 18. 
GLycIMERIS arctica. Desh. 2d ed. Lamarck, tom. vi, p. 70, 1835. 
— Norvecica. Gray. List Brit. Moll., p. 63, 1851. 
Panopra Grycrmerts. Bean. Mag. Nat. Hist., vill, p. 562, figs. 50, 51. 
* Etym. Panope, one of the Nereids. Panopea, Hubn. 1816, a genus of Lepidoptera. 
37 
