410 MOLLUSCA. SIPHONIDA. 



A A. Destitute of a secreted calcareous tube. 



a. Ligament external. 



Pholad.*. With accessory valves, or gaping ven« 

 trally. 

 Pholas. 

 Gastrochsena. 

 SolenidjE. No accessory valves ; gaping only at the 

 extremities. 

 Solen 



Sanguinolaria. 

 Hiatella. 

 Panoptea. 

 (Glycemeris) 



a a. Ligament internal. 

 Mya. 

 Lutraria. 

 Sphenia. 

 Pandora. 

 Galeoxna. 



