127 



CLAVAGELLA Lamarck. 



Gen. Char. A bivalve vs^hose valves are contained 

 within a shelly vagina, with the surface of 

 which one of them only is incorporated ; va- 

 gina claviform, furnished with tubes about its 

 larger end. 



Until the recent species of this Genus was discovered*, 

 there remained some room to doubt the fact of one of 

 the valves of the shell being united to the shelly tube, 

 a want of symmetry that is very difficult to admit with- 

 out good evidence, and to which we know of nothing 

 analogous. The two Genera of the same family be- 

 tween which this would naturally arrange, are Asper- 

 gillum (commonly called theWatering-pot) and Gastro- 

 choena, which probably includes all the Fistulanae of 

 Lamarck that really have shelly tubes, and do not be- 

 long to Teredo) : the first of these has two equal valves, 

 both so united to the tube as to form part of it, the latter 

 has both the valves loose and also equal ; thus the cir- 

 cumstance of one valve being attached is very remark- 

 able. The form of the valves in Clavagella and also 

 in Aspergillura is somewhat like those of Mya : the two 

 Genera, however, differ in the tube, that of Aspergillura 

 having besides a fringe of tubes a number of simple 

 perforations in a convex disk, which do not exist in 

 Clavagella : in most of the species of Clavagella the 

 small tubes are irregularly scattered over the larger end 

 of the principal tube or vagina, but in one they are in a 

 circle and regularly branched ; this species consequently 

 leads to Aspergillum. Most of the species require to 

 be attached to some solid body for their support, or are 

 imbedded in porous stones : some, however, seem to be 

 free, and not one probably is capable of boring a hole 

 for itself, as all the Gastrochoenae and the Fistulanae do. 

 We have shortened the Generic Character in conse- 

 ciuence of its being too precise a description of one spe- 

 cies, but trust it is still sufficient to exclude every other 

 Genus. 



* See Sowerby's Genera of Shells, " Clavagella aperta." 



