The above is a figure of the Heart Isocardea, (I. cor,) which is also a member of the Clam family, and one of the most elegantly-shaped shells in the whole range of Conchology. It is a native of the Mediterranean and other seas of Europe, and has been taken in deep water on the West coast of Ireland. We complete this group with a representation of the curious Arcadæ family, or Ark shells, as they are commonly called, because one of the species was thought to resemble the ark built by Noah. Mr. Swainson tells us that the animals of these shells affix themselves to other bodies by a particular muscle, which is protruded through the gaping part of the valves; they also adhere, when young, by means of the bissiform epidermis, or bissus-like outer skin: this species is a native of the Atlantic Ocean and the seas of Europe. The Antique Ark, (A. antiqua,) is very like the Common Cockle, being of a white colour, and heart-shaped. We give below a representation of this shell, and also of the shell of the pretty little Pearly Trigonia, (T. margaritacea,) included in the Arcadæ family; this is a rare species, found only in the seas of New Holland.
SCALLOP SHELLS.
Several species of Scallop Shells are found scattered about on our shores; they belong, as before stated, to the family Pectinidæ, the meaning of which term has been already explained. These shells were called by Cuvier “the Butterflies of the Ocean,” on account of the various and beautiful colours which they exhibit. Some of them are exceedingly thin, and brittle as glass; one species found in the Arctic regions, is as transparent as that substance, and is therefore called P. vitreus, from the Latin for glass, which is vitreum. One of the commonest of our native Scallops is the St. James’ Cockle, (P. Jacobœus;) this shell is found in great plenty along our southern coasts; it is often referred to by old writers, on account of having been commonly worn in the hats of pilgrims to Palestine, or the Holy Land, as the scene of our Saviour’s life and death was called. Sir Walter Raleigh, in his poem called “The Pilgrimage,” thus enumerates the different articles considered necessary for a Palmer, as these pilgrims were termed:—
“Give me my scallop shell of quiet,
My staff of faith to lean upon,
My scrip of joy, (immortal diet,)
My bottle of salvation,
My gown of glory, hope’s true gage,