"The herring it loves the merry moonlight,
The mackerel it loves the wind;
But the oyster it loves the dredger's song,
For it comes of a gentle kind."
The Scallop-shell (Pecten) is round, nearly equal-sided, resting on the right valve, which is more convex and marked with radiating ribs. Linnæus made the mistake of confounding with the Ostrea a great number of shells, which, by their channeled edges and surfaces, strongly reminded one of the arrangements of the teeth of a comb, whence their name of Pecten. They were well known to naturalists long before the time of Linnæus, under the name of Pilgrims' shells, a name which came into use from the practice which prevailed among pilgrims in the middle ages—we know not why—of ornamenting habits and hats with the valves of some of the species.
The shell of the Pecten is in general nearly circular, more or less elongated, and terminated towards the summit in a straight line, forming a sort of triangular appendage called the ear, to which the hinges are attached. The valves are very regular, but with no resemblance to each other. In some species, the shell of which is closely shut, the lower valve is more or less convex than the upper one. In others, both valves are convex. The hinge is without teeth, and the ligament, which is intended to close the shell, is inserted into a triangular depression or dimple. The retractile muscle is unequal, and nearly central. The valves are not nacred inside, and are formed on their exterior surface of numerous fluted channels, which spring from a lobe more or less pointed at the summit, diverging towards the circumference. The edges are sometimes smooth, as in the Watered Pecten (P. pseudamussium, Fig. 175), but more frequently they are formed in strips or scales, as in the Smooth-shelled Pecten (P. glaber, Fig. 176). Upon the whole, however, the Pectens are very variable, but always elegant in form; the colours are frequently lively and brilliant. In Pl. XIV., some of the most striking forms are represented, as in Fig. I., the Ducal Mantle (Pecten pallium), an inhabitant of the Indian Ocean, remarkable for its elegant form, its twelve radiating stripes, diverging towards the circumference, the horizontal furrows of its salient scales, and the striking distribution of its white spots upon a bed of red and brown marble; Fig. II., the Purple Pecten; Fig. III., the Coral Pecten; Fig. IV., the Tiger Pecten; Fig. V., the Foliaceous Pecten; and Fig. VI., the Northern Pecten.
Fig. 175. Pecten pseudamussium (Chenu).
Fig. 176. Pecten glaber (Linnæus).