208 BULLETIN OF THE 



Amusium Megerle von Muhlfeld, Entwurf. (etc.) Mag. d. Gesellschaft f. Natnrh. 

 Freunde zu Berlin, V. i. p. 69, 1811. 

 Bolten, M'u8. Bolt., ed. ii. p. 116, 1819 (name only). 

 Schumacher, Essai, p. 117, 1817; P. pleuronectea (full description). 

 xAinium b, Link, Beschr. Rostock Samml., part 3, p. 156, 1807 ; P. japoniatm. 

 Amusium Herrmannsen, Ind. Gen. Mai., L p. 47, I8i6 ; = Amusium Klein corr. 

 H. & A. Adams, Gen. Rec. Moll., II. p. 564, 1858. JeEEreys, Annals 

 and Mag. Nat Hist., Nov. 1876, p. 424 ; P. Z. S. 1879, p. 661. 

 Pleuronedia Swainson, Malacol., p. 388, 1840, P. pleuronectes (description). 



Chenu, Man. de Conchyl., II. p. 187, 1862 ; P. japonica. Jeffreys, in 

 Wy ville-Thomson, Depths of the Sea, p. 464, 1873. 

 Amusium Woodward, Manual, ed. ii. p. 412, 1866. Stoiiczka, Pal. Indica, IIL Cret. 

 Pelecypoda, p. 426, 1871. 



Shell smooth or very slightly sculptured externally ; valves gaping at the 

 sides, nearly equally convex, with radiating internal ribs ; ears subequal, small ; 

 notch obsolete or none ; hinge line straight ; margin entire ; shell free (byssif- 

 erous ?). Type Pecten pleuronectes L. 



The name Amusium is of uncertain meaning or origin, but appears to 

 have been in use colloquially at least two hundred years ago to denominate 

 the " compass shell " or " flounder scallop." It was used by Rumpf in his 

 Treasury of Rarities from Amboyna, as pointed out by Dr. Jeffreys, and 

 probably here made its first entry into print. It was adopted by Klein, in his 

 curious and very unequal work on shells, ^br one of the groups in which he 

 placed the Pectens of Lamarck and later authors ; it was referred to by Martini, 

 and doubtless by other non-binomial writers, whom it would be profitless to 

 search out. 



Its first entry into binomial scientific literature (if an auctioneer's sale cata- 

 logue without figures or descriptions may be so called) was in the obscure 

 pamphlet usually known as the Museum Boltenianum, of which a new edition 

 was publishtd in 1819. The first place where the name Amusium received a 

 description entitling it to recognition was in Schumacher's Essai, in 1817, 

 though Link had characterized the group as a section of his genus Pedinium 

 (= Pecten) ten years previously. Apparently in ignorance of Schumacher's 

 work, Swainson described it as a new genus in 1840, under the name Pleuro- 

 tiectia, which was adopted later by Chenu. Herrmannsen and others have 

 suggested that the name should be spelled Amussium, but the uniformity of 

 previous usage and the uncertainty in regard to its derivation seem to render 

 this inadvisable. 



The characters which separate this group from the typical genus are chiefly 

 cnnchological. The byssus (if any exists, for so far I have not been able to 

 find any) passes between the gaping valves, and the notch, which usually exists 

 in the very young, is not found in the adult form, which would seem to have 

 discarded the byssus entirely, and supplied its place by using the terminal 

 sucker of the foot, which is large and expanded. The group frequents deep 



