446 MOLLUSCA. 
Perna nana, Goutp; Proceed. Boston Soc. Nat. Hist., iii. 312. 
Nov. 1850. Expedition Shells, 92. 
SHELL small, solid, elongated, rounded posteriorly and at base, con- 
cave anteriorly, adunque at tip: surface generally smooth and shining, 
squamous towards edge, coal black. Interior slaty black, or black- 
lead colour, silvery under beaks, darker towards periphery: hinge 
area very thick: teeth, about six: byssus aperture formed by a broad 
inflexure of the anterior margin: calcareous edge narrow and pale: 
muscular impressions deeply marked. 
Length three-fifths of an inch; height three-fourths of an inch; 
breadth one-fourth of an inch. 
Inhabits the Feejee Islands, under stones. Drayton. 
The solidity and colour of this little species will not admit of its 
being confounded with any other species. It bears the marks of 
mature age. 
Figures 556, 556 a, inside and outside of the shell. 
PERNA EREMITA (Gould). 
T. fragilis, exaluminata, variabilis, dolabrata, vulsellata, unguiformis, 
pectiniformis et omnimode distorta, plerumque radiatim rugoso-striata 
et in gunioribus rufo-lineata ; antrorsum plus minusve arcuata: mar- 
garita argentea; limbo cortical ampliato, foliaceo, stramineo, vitreo : 
margine cardinali feré horizontal, sex ad octo sulcato ; fissura byssah 
profunda. 
Perna eremita, Goutp; Proceed. Boston Soc. Nat. Hist., iii. 311. 
Nov. 1850. Expedition Shells, 92. 
SHELL small, thin, fragile, very irregular, conforming itself to its 
places of abode: normal form pectiniform, subcircular, with a short, 
straight, dorsal margin, but sometimes much elongated, like Malleus. 
Colour pale greenish horn-colour, near the beaks radiated with bery]- 
green. Young specimens, which have been protected from injuries, 
