PHOLAS. 



TESTA transversa, oblonga, aequivalvis, inse- 

 quilatera, utroque latere hians, hiatu antico 

 plerumque maximo, interdum ferh elauso ; valvis 

 accessoriis difformibus ssepius instrueta; Car do 

 utriusque valvae dente longo curvo, infra margi- 

 nem umbonalem reflexum prominente. (Liga^ 

 mentum nullum^ aut minnimum^ internumi ) 



Pholas and Gastrochcena together constitute Lamarck's 

 family of Pholadaires, though he appears to have enter- 

 tained some doubt of the propriety of thus uniting those 

 two genera into one family, and we have endeavoured 

 formerly to show that Gastrochaena belongs rather to the 

 TuhicoUes than to the Pholadaires. We may now perhaps 

 without impropriety propose the following question; 

 Would it not have been more consistent with the rules of 

 association apparently entertained by Lamarck if he had 

 united the Petricolce, Fetiermipes, and other terebrating 

 Conchifera, which do not form a shelly tube, with Pholas 

 in one family, and have placed Gastrochcena with Teredo 

 JFistulana, Aspergillum and others which enclose their two 

 valves in a shelly tube open at one or both ends? We 

 may also ask if the commonly called Pholas papyracea (a 

 shell which has lately become pretty generally known) 

 may not be considered as the type of the connecting link 

 between the two families, inasmuch as it bas the general 

 form and characters of a Pholas and apparently com- 

 mences a shelly tube at one end? 



Pholas is one of the few genera which bas always 

 remained nearly entire, excepting that occasionally a 

 species of some other distinct Genus may have been in- 



