CONCHIFERA. 903 
are formed by the siphonal orifices when the animal continues 
elongating, after having fixed its valve and ceased to burrow; 
or perhaps, in some instances, when it is compelled to lengthen 
its tubes upwards by the accumulation of sediment. Brocchi 
mentions that on breaking the tube of the fossil C. echinata, he 
sometimes found the shell of a Suwicava or Petricola beside the 
loose valve of the Clavagella, into whose tube they must have 
entered after its death. CC. elongata is found in coral; C. 
australis lives at low tide, and spirts out water when alarmed. 
Distribution, 6 species. Mediterranean, Australia, Pacific :— 
11 fathoms. 
Fossil, 14 species. U. Greensand—. Britain, Sicily, 
Southern India. 
ASPERGILLUM, Lam. Watering-pot shell. 
Type, A. vaginiferum, Pl. XXIII., Fig. 18. 
Synonym, Clepsydra, Schum. 
Shell small, equilateral, cemented to the lower end of a shelly 
tube, the umbones alone visible externally; tube elongated, 
closed below by a perforated disk with a minute central fissure ; 
siphonal end plain or ornamented with (1—8) ruffles. 
Animal elongated ; mantle closed, thickened and fringed with 
filaments in front; foot conical, anterior, opposed to a minute 
sht in the mantle; palpi lanceolate; gills long, narrow, united 
posteriorly, continued into and attached to the branchial siphon. 
Distribution, 21 species. Red Sea, Java, Australia, New 
Zealand ; in sand. 
Fossil, 1 species. (A? Leognanum, Hoeening. Miocene, Bor- 
deaux. ) 
HUMPHREYIA, Gray. 
Shell developed in the substance of the siphons, which grow 
with the ventral side uppermost. 
Distribution, 1 species. South Sea. 
Famity X XI.—PHOLADIDA. 
Shell gaping at both ends ; thin, white, brittle, and exceedingly 
hard ; armed in front with rasp-like imbrications ; without hinge 
or ligament, but often strengthened externally by accessory 
yalves; hinge-plate reflected over the umbones, and a long 
curyed muscular process beneath each; anterior muscular im- 
pression on the hinge-plate; pallial sinus very deep. 
Animal club-shaped, or worm-like; foot short and truncated ; 
