118 TRANSACTIONS, NATURAL HISTORT SOCIETY OF GLASGOW. 



had dredged them in 1893 off the Isle of Man, between Port- 

 Erin and the Calf, in about 25 or 30 fathoms. The Liverpool 

 Marine Biological Association has a station at Port-Erin, and it 

 was whilst some members of the committee were working out 

 the marine fauna of the district that the shells were discovered. 

 Only a few at most were obtained, some being sent to Canon 

 Norman and to Mr. J. T. Marshall, who' both identified the 

 mollusc as P. incomparabilis. The shell has suffered from a 

 frequent change of name. Forbes and Hanley, in their British 

 Mollusca, call it Pecten furtivus of Loven; but Jeffreys, in his 

 British Conchology, names it Pecten testae of Bivona, in honour 

 of Signor Testa, a conchologist at Panormo, in Sicily. The 

 Revised List of the British Marine Mollusca, prepared by a 

 committee of the Conchological Society of Great Britain and 

 Ireland in 1901, restored the earlier name, Pecten incompara- 

 bilis of Risso. 



" Jeffreys {Brit. Conch., vol. ii., p. 68) says — ' This beautiful 

 species differs from P. tigrinus, with which it is sometimes 

 found, in the following particulars : — The shell is broader, flatter, 

 and thinner; the ribs, when they occur, are scaly or prickly; 

 the punctures are very strongly marked and arranged in 

 squares; the beaks are much less prominent and raised; the 

 ears are not so unequal; and the inside margin is seldom 

 crenulated. Forbes and Hanley considered it to be a variety 

 of P. striatus, but Malm has satisfactorily shown some of the 

 points of difference between these two species. 1 have never 

 seen an intermediate form, although I have examined many 

 hundred specimens of P. striatus and about fifty of P. testae, 

 with a view to the comparison. The present species has some 

 of the sculpture of P. tigrinus and the shape of P. striatus. 

 The colouring of P. testae is more bright and vivid than that 

 of the other two.' 



" The shell is one of our rarest British Pectens. Forbes and 

 Hanley record it as having been obtained in Loch Fyne by 

 M'Andrew, at Gahvay by Barlee, and at Exmouth by Clark. 



" Jeffreys gives Shetland (Lerwick), in 40 and 50 fathoms ; 

 Skye; Larne, County Antrim; Birterbuy Bay, County Galway; 

 and Guernsey — all discovered by himself. 



'■ Since the publication of the works of these authors, the 



