ACEPHALA. AB5 
into fine filiform appendages. Interior deep claret-red, even blackish 
in old specimens; edge yellowish. 
Length an inch and a quarter; height three-fourths of an inch ; 
breadth five-eighths of an inch. 
Inhabits the Feejee Islands. 
A small, elongated species, with its dorsal edge obtusely angular, 
but best distinguished by its peculiar lurid exterior colouring, and its 
reddish molybdzna-coloured interior. Young shells have a straw- 
coloured disk. 
Figure 563, side of the shell, exterior and interior ; 563 a, dorsal 
view. 
Myrtitus (Modiolarca) pustLius ( Gould). 
1. parva, transversa, subcylindrica, ovals, solida, concentricé striata ; 
marginibus subparallelis ; latere antico truncato, angulo ventral ob- 
tuso ; latere postico late rotundato ; apicibus tumidis, subterminalibus, 
contortis ; colore cinereo, vel rubro-tincto. 
Mytilus (Modiolarca) pusillus, Goutp; Proceed. Boston Soc. Nat. 
Hist., in. 345. Dec. 1850. Expedition Shells, 59. 
SHELL minute, thick and solid, transversely oval, beaks nearly ter- 
minal, elevated and tumid, somewhat excurved, like Isocardia; the 
whole shell inflated, subcylindrical; dorsal and basal margins nearly 
parallel; posterior end broadly rounded; anterior end vertical; basal 
angle obtuse; surface concentrically striate; epidermis very delicate, 
colour pale cinereous, sometimes tinted reddish ; interior clouded brown, 
and an intense red-brown; hinge margin intense blood-red; a single, 
obsolete, apicial, oblique, coaptate tooth in each valve, continued pos- 
teriorly, so as, with the posterior edge, to form a ledge for the ligament 
simulating sometimes an elongated lateral tooth; the apicial tooth 
sometimes bifid. 
Length one-fifth of an inch; height one-eighth of an inch. 
