326 MANUAL OF THE MOLLUSCA. 



2 inches deep and | inch diameter ; the external orifice is hour-glass shaped, 

 and lined with a shelly layer which projects slightly. When burrowing in 

 oyster-sheUs it often passes quite through into the ground below, and then 

 completes its abode by cementing such loose material as it finds into a 

 flask-shaped case, having its neck fixed in the oyster-shell ; in some fossil 

 species the siphons were more separated, and the flasks have two diverging 

 necks. The siphonal orifices are rarely 4-lobed ; PI. XXIII. fig. 15 a. 



Blstr. 10 sp. W. Indies, Brit. Canaries, Medit. Red Sea, India, Mauri- 

 tius, Pacific Ids. Gallapagos, Panama : — 30 fms. 



Fossil, 20 sp. Inf. Oolite — . U. States, Europe. 



Sub-genus. Chaena, Retz. 1788. C. mumia. PI. XXIII. fig. 16. 

 ( = Fistulana clava. Lam.) Shell elongated, contained within a shelly tube ; 

 posterior adductor nearly central, with a pedal scar in front; siphonal inflec- 

 tion angular, with its apex joining the pallial line. Tube round, straight? 

 tapering upwards, transversely striated, closed at the lower end when com- 

 plete, and furnished with a perforated diaphragm behind the valves. Dlsir- 

 Madagascar, India, Philippines, Australia ; bun-owing in sand or mud. 



Fossil, Inf. Oolite — . U. S. Europe, S. India. 



Clavagella, Lamarck. 



Ex. C. baciUaris, PI. XXIII. fig. 17. 



Shell oblong, valves flat, often irregular or rudimentary, the left cemented 

 to the side of the burrow, when adult, the right always free ; anterior mus- 

 cular impression small, posterior large, pallial line deeply sinuated. Tube 

 cylindrical, more or less elongated, sometimes divided by a longitudinal par- 

 tition; often furnished with a succession of siphonal fringes above, and 

 terminating below in a disk, with a miuute central fissure, and bordered with 

 branching tubuli. 



Animal with the mantle closed in front, except a minute slit for the foot, 

 and furnished with tentacular processes ; palpi long and slender ; giUs 2 on 

 each side, elongated, narrow (floating freely in the branchial siphon ?) 



Some specimens of the recent C. aperta have 3 frills to their tubes, and 

 C. hacillaris has twice that number occasionally. They 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 com- 

 pelled 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 Saxicava or Petricola beside the loose valve 

 of the Clavagella, into whose tube they must have entered after its death. 

 C. elongata is found in coral ; C. australis lives at low tide, and spirts out 

 water when alarmed. Bistr. 6 sp. Medit. Australia, Pacific:— 11 fms. 



Fossil, 13 sp. U. Green-sand — . Brit. SicUy, S. India. 



