410 MOLLUSCA. SIPHONIDA. 



A A. Desiilnie of' a secreted calcareous tube, 

 a. Ligament external. 



PholadjE. With accessory valves, or gaping ven- 

 traliy. 

 Pholas. 

 Gastrochaena. 

 SoLENiD^E. No accessory valves ; gaping only at the 

 --^ extremities. 



Solen 



Sangninolaria. 

 Hiatella. 

 Panopaea. 

 (Glycemeris) 



a a. Ligament internal. 

 Mya. 

 Lutraria. 

 Sphenia. 

 Pandora. 

 Galeoma. 



