PHOLADID&. 133 
Genus, PHOLADIDEA—Turton. 
Siphons with horny or shelly pieces at their base, the branchial 
siphon cirrated, the anal plain at the end. Shell widely gaping in front, 
but closed by a callous plate ; two dorsal pieces, straight. 
P. spathulata, Sowerby, P.Z.S., 1849, p. 162; Reeve, Conch. Le. 
(Pholas,) f- 45. Shell elongated, closed, obliquely divided ; anterior 
part radiately ribbed, sub-angulated ; posterior part concentrically lightly 
striated, subtruncated, protected at the margins by an integument, pro- 
duced at the end into a horny cup with spathulate sides; two equal 
lamin, bilobed posteriorly, elongated anteriorly at the umboes 
(Sowerby.) 
As far South as Waikouaiti. 
P. tridens, Gray, Dief. N.Z., ii., p. 254; Voy. Erebus and 
Terror, pl. 2, f.8; Reeve, Conch. Lc., f: 38. Ovate, with a deep central 
groove ; front half with close waved concentric ridges ; hinder half with 
distant regular concentric grooves; front gape large, broad, ovate, at 
length closed up, the two hinder processes forming together a cup about 
as long as broad, each furnished with a sub-marginal and central rib 
(Gray. ) 
According to Sowerby, this species comes from Monte Christo. 
Genus, THEREDO—Linneus. 
Animal worm-like ; siphons furnished at their extremity with two 
shelly styles or pallettes ; umbonal muscle covered only with a coriace- 
ous epidermis, and not protected by shelly accessory valves. Shell 
globose, gaping anteriorly and behind ; valves trilobate, divided by a 
single transverse groove ; hinge margins inflexed anteriorly ; interior of 
valves furnished with a long curved process. Living at the inner extre- 
mity of a burrow, partly or entirely lined with shell. 
T. antarctica, Hutton, C.M.M., ~. 59. Shell globose, the valves 
tri-lobed, ear-shaped behind, lower lobe produced, acute, the interior 
process for attachment of the pedal muscle, dilated at the end ; anterior 
end deeply notched, the notch forming a right angle ; outside smooth 
behind, striated in front by lines parallel to the edge of the notch, the 
strie on the lower and posterior part being finer than those on the 
upper and anterior part, and the interstices with minute cross striz, 
while the interstices of the upper strie are smooth; tube obsolete ; 
pallettes elongate, slightly curved, penniform. 
Auckland to Dunedin. 
Sub-Order—Myacea. 
Siphons long, united ; gills not extending into them. Shell gaping 
behind, with an inner hinge cartilage. Shell and siphons covered with 
periostracum. 
