14 
PACIFIC SCIENCE, VoL XXI, January 1967 
adductor muscle scar group. 
DISTRIBUTION: As fossils from T-l (1 valve), 
T-7 (1 valve), T-ll (2 valves; 3 entire), T-l 2 
(13 valves; 1 entire), AR (1 valve; 1 entire), 
and S-23 (3 valves). Brady (1880:59) reports 
this species from two dredgings; one at Torres 
Straits, 11° 35'S, 144° 3'E, at 155 fathoms, and 
one near Hawaii at 40 fathoms. As "young 
Pliocene” fossils from Timor, Netherlands 
East Indies (Fyan, 1916:78). Found living at 
HA (Is) at 5 fathoms. Egger (1901) reports 
a single valve off the west coast of Africa at 370 
fathoms (redeposited?). 
discussion : Sexual dimorphism is subtly 
manifested by a taller male. The similarity of 
these specimens to Bairdia attenuata of Brady 
(1880) and Fyan (1916) is close, though the 
Hawaiian specimens dealt with here show a 
lower caudal process. Brady (1880), when de- 
scribing the species, apparently illustrated forms 
not from Hawaii. Dr. Bate (personal communi- 
cation) of the British Museum (Natural His- 
tory) , who compared some of the present speci- 
mens with Brady’s types, also notes that the 
former have a more upturned posterior and 
anterior. However, similarities in morphology 
and the nature of the adductor scar pattern, i.e., 
size, shape, configuration, and position, suggest 
that these specimens are conspecific with Brady’s 
form. 
