Pvn H,i I'UitlS

ARCA. 171
stand in the same relation to genera as varieties to spe-
cies, is the point at issue. I am not in favour of this
intermediate sort of classification, and believe it would
lead to unnecessary confusion, and to a redundancy of
names for the same object.. "Area (subg. Cucullaza)
pectunculoides " is not easy to pronounce, or even to
remember, on account of the parenthetical epithet.
Such a mode of subgeneric nomenclature appears to me
quite opposed to the spirit and simplicity
of the bino-
mial system ; and it may not be desirable to follow the
example of some modern painters in reviving
a state of
things that has passed away and become obsolete, by
now having a pre-Linnean school. The animal of Area
constituted the genus Daphne of Poli.
A. Shell slightly inequivalve : teeth few in number, set either
obliquely or in the line of the hinge-plate, and arranged
in two rows, one at each end of the plate, besides nume-
rous crenulations in the middle across the plate.
1. Arca pectunculoi'des *, Scacchi.
A. pectunculoides, Scacchi, Ann. civ. d. due Sicil. vi. p. 82. A. raridera-
tata, F. & H. ii. p. 241, pi.
xlv. f. 8.
Body reddish-brown : foot long and narrow, when in motion
resembling that of a Gasteropod : byssus rather long, horny,
and consisting of a single cylindrical thread.
Shell obliquely rhomboidal, describing in its contour a segment
equal to nearly two-thirds of a circle, tumid, thin, rather
glossy ;
the right valve (or that which has the anterior side to
smaller than
and en-
the right hand of the observer) is unmistakeably
the left valve, the margin of which slightly projects
closes the opposite valve : sculpture, numerous fine and sharp
longitudinal ribs, radiating from the beaks, and equally numerous
but less raised transverse or concentric ribs, which cross
the other striae and give the surface a regularly reticulated
* Like Pectunculus.
i2