208 BULLETIN OF THE 
Amusium Megerle von Muhlfeld, Entwurf. (ete.) Mag. d. Gesellschaft f. Naturh. 
Freunde zu Berlin, V. i. p. 59, 1811. 
Bolten, Mus. Bolt., ed. ii. p. 115, 1819 (name only). 
Schumacher, Essai, p. 117, 1817; P. pleuronectes (full description). 
Pectinium b, Link, Beschr. Rostock Samml., part 3, p. 156, 1807; P. japonicum. 
Amussium Herrmannsen, Ind. Gen. Mal., I. p. 47, 1846;== Amusium Klein corr. 
H. & A. Adams, Gen. Rec. Moll, II. p. 554, 1858. Jeffreys, Annals 
and Mag. Nat. Hist., Nov. 1876, p. 424; P. Z. S. 1879, p. 561. 
Pleuronectia Swainson, Malacol., p. 388, 1840, P. pleuronectes (description). 
Chenu, Man. de Conchyl., II. p. 187, 1862; P. japonica. Jeffreys, in 
Wyville-Thomson, Depths of the Sea, p. 464, 1873. 
Amusium Woodward, Manual, ed. ii. p. 412, 1866. Stoliczka, Pal. Indica, III. 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 Amusiwm 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, for 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 published in 1819. The first place where the name Amusiwm 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 Pectinvum 
(= Pecten) ten years previously. Apparently in ignorance of Schumacher’s 
work, Swainson described it as a new genus in 1840, under the name Pleuro- 
nectia, 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 
conchological. 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 
