Class—Lamellibranchiata. 
No head, nor eyes. Shell composed of two valves, occasionally with 
supernumerary pieces ; heart with two chambers ; nervous system with 
three principal pairs of ganglia. Gills lamellar, two on each side. 
Usually dicecious. 
ORDER—IsoMYA. 
Adductor scars two, equal, or sub-equal on each valve. 
SECTION—SINUPALLIATA. 
Pallial line with a deep sinus. 
Sub-Order—Pholadacea. 
Mantle closed, but allowing two more or less elongated siphons to 
pass out, which are contiguous at the base ; the inferior with two pairs 
of branchiee in it. . 
FAMILY—-PHOLADID. 
Animal symmetrical, club-shaped or worm like. Palpi elongate, 
linear. Mantle partly exposed, closed in front, except an aperture for 
the foot ; siphons large, elongated, united nearly to their ends ; orifices 
fringed. Gills narrow, prolonged into the branchial siphon, attached 
throughout, closing the branchial chamber. Foot short and truncated. 
Shell gaping at both ends, thin, white, brittle; hinge plate reflected 
over the umbones, and a long curved muscular process beneath each ; 
anterior muscular impression on the hinge plate; pallial sinus very 
deep. 
Boring holes in wood and rocks. 
Genus, BARNEA—Risso. 
Shell ovato-oblong; gaping anteriorly; a single lanceolate dorsal 
accessory piece ; hinge margin reflected. Siphons naked at their base, 
both branchial and anal cirrated. 
B. similis, Gray, Dief. N.Z, ii, p. 254; Reeve, Conch. Le. 
(Pholas,) f. to. Rather elongate, acute in front, tapering behind ; with 
concentric lamine, which are higher and closer together at the anterior 
end, where they are crossed by radiating lines ; sub-spinose at the 
crossings ; dorsal plate elongate, acute in front, truncated behind. 
Height, 1; length, 2°5. 
Common in the North Island. Waikouaiti. 
