CLAVAGELLA. 337 



Genus CLAVAGELLA, Lamarck. 



Shell oblong, irregular, inequivalve, right valve always 

 free, the left imbedded in the dilated, hind part of the tube. 

 Muscular impressions two, the anterior small, the posterior 

 large ; pallial impression with a deep sinus. 



Tube testaceous, cylindrical, more or less elongated, pos- 

 teriorly attenuated and open ; the margin of opening simple, 

 or furnished with siphonal fringes ; the anterior or lower 

 end of tube ovate, compressed, club-shaped, simple or sur- 

 rounded by spiniform tubes, and with a minute central fissure, 

 sometimes incomplete. 



Syn. Bryopa, Gray. 



Ex. C. aperta, Sowerby, pi. 91, fig. 3. Shell, C. aus 

 tralis, 3, a, 3, b. Tube, C. australis, fig. 3, c. 



The mantle in Clavagella is furnished with tentacular 

 processes, which form the branching tubuli at the fore part 

 of the tube; the frills or fringes which ornament the hind 

 part of the tube are formed by the siphonal orifices at 

 various stages of growth of the animal ; in other respects 

 the animal resembles those of the other genera of the family, 

 the palps being elongate and slender, the mantle closed, the 

 siphons united and extended, and the gills being prolonged 

 into the branchial tube. Most of the recent species of Cla- 

 vagella burrow in stone and coral, and the tube is incom- 

 plete and without any spiniform processes ; Australia, the 

 Mediterranean, and the Pacific furnish us with examples. 



