456 MOLLUSCA. 
Inhabits Tierra del Fuego. 
This curious little shell is interesting from its being a representa- 
tive, from the southern seas, of a form not uncommon in northern 
waters. 
Figures 585, 585 a, 585 0, lateral, dorsal, and hinge views of the 
shell, enlarged ; 585, natural size. 
PrcTEN L&TUS (Gould). 
T. ovato-triangularis, ventricosa, equivalvis, dilute rosea albo quinque 
ad sex-radiata: margine ligamentah obliquo, auriculis valde inequah- 
bus, obliquis ; auricula byssica profunde fossato-emarginatd, radiatim 
sulcato-costata, costis numerosis inequalibus arguté muriculata: intus 
allido-incarnata. 
Pecten letus, Goutp; Proceed. Boston Soc. Nat. Hist., i. 345. 
Dec. 1850. Expedition Shells, 95. 
SHELL rather small and thin, nearly equivalve, longer than broad, 
ventricose, pale rosaceous, with three or four pale rays: hinge margin 
oblique; auricles very unequal, and very strongly defined by the ab- 
rupt or even channeled border of the body of the shell; short ear 
quite small, oblique, forming an obtuse angle; byssal auricle large, 
oblique, nearly equilateral, forming an acute angle; byssal fissure 
very large, quadrilateral, denticulate, isolated by a deep, broad, smooth 
groove from the apex, leaving a long, tomahawk-shaped, nearly iso- 
lated, radiately grooved auricle. On the opposite valve, against the 
notch, is a prominent tubercle by an inflection of the margin. Sur- 
face everywhere furrowed with radiating grooves, forming numerous 
unequal rib striz, rigid with fine, muricate scales; the two valves 
sculptured nearly alike, the pale one a little the finest. Interior white, 
tinted flesh-colour. 
Length an inch and four-fifths; height three-eighths of an inch; 
breadth an inch and three-fourths. 
Inhabits New Zealand. 
