56 



Among the former are ranged globular, shining ocelli ; no si- 

 phonal tubes ; foot small, cylindrical, with a byssal groove from 

 which a weak byssus is spun, mostly when the animal is young ; 

 mouth surrounded by folia ceo us leaflets and two pairs of labial 

 tentacles, which are smooth externally, pectinated internally ; 

 branchial leaflets equal, each pair partially doubled on itself. 

 (Forbes.) 

 Shell ; rarely affixed, more or less orbicular, regular, inequivalve, 

 nearly equilateral, unequally auriculated on either side of the 

 hinge, sometimes a little gaping, mostly symmetrically rayed 

 with ribs or ridges ; umboes approximated, without any inter- 

 vening area ; hinge toothless, with a marginal ligament, and a 

 ce7itral internal solid ligament in a deep triangular pit ; a more 

 or less distinct byssal sinus in one valve. 



In all collections of British shells the Pectens occupy a conspicuous 

 place as the most gaily painted of bivalves ; but the British species, with 

 their attractive varieties of colour and pattern, are but as the bramble 

 beside the rose when compared with the Harlequins, Ducal Mantles, and 

 other elaborately scaled and intensely brilliant species of exotic climes. 

 Lamarck, while enumerating as many as fifty-nine species of Pecten, de- 

 scribed it, in the plenitude of his enthusiasm, as " le beau et immense 

 genre." Now we have even finer species, and three times as many ; and 

 so nicely balanced are the general affinities between them, that concho- 

 logists have failed to establish more than two received subdivisions, — the 

 sections Vola and Amusium. 



The Pectens live at various depths, and move, either alone or in groups, 

 with a jerking motion by the rapid opening and shutting of their valves.* 

 When at rest they spin a slight byssus from the foot. The shell, which is 

 of lighter substance than in the preceding genera, is developed in radia- 

 tions, like a pleated fan, with the utmost symmetry and order, and the 

 painting of the lower valve is oftentimes little less brilliant than that of 

 the upper. By the older writers Pectens were called indifferently Scallops, 

 and sometimes Cockles ; and the Pecten Jacobceus, named in honour of St. 

 James, was worn as an emblem by the pilgrim journeying to the Holy 



* Dr. Landsborough, the well-known Scottish naturalist, writes : — " We observed on a sunny 

 September day in a pool of sea-water, left on Stevenston Strand by the ebbing tide, what we at 

 first thought some of the scaly brood at play. On close investigation, however, we found that 

 it was the fry of Pecten opercularis skipping quite nimbly through the pool. Their motion was 

 rapid and zigzag, very like ducks in a sunny blink rejoicing in the prospect of rain. They 

 seemed, by the sudden closing and opening of their valves, to have the power of darting like an 

 arrow through the water. One jerk carried them some yards, and then by another sudden jerk 

 they were off in a moment in a (Liferent tack." — Scottish Christian Herald, vol. ii. p. 165. 





