BRITISH MARINE TESTACEOUS MOLLUSCA : 



SYNOPSIS OF THE FAMILIES AND GENERA OF THE BRITISH TES- 

 TACEOUS ACEPHALA, GASTEROPODA, AND CEPHALOPODA, 

 DISTRIBUTED IN SIX DIVISIONS, ON THE BASES OF SEXUAL 

 ORGANIZATION. 



Eirst Division. 



ACEPHALA PALLIOBRANCHIATA. 



Hermaphrodita, sine concubitu. 

 TEREBRATULID.E Hypothyris. 



Terebratula. 



Argiope. 

 CRANIAD.E Crania. 



Second Division. 



ACEPHALA LAMELLIBRANCHIATA. 



Hermaphrodita, sine concubitu. 



* Mantle open, no tubes. 



ANOMIAD.E Anomia. 



PECTINID^E Pecten. 



OSTREAD.E Ostrea. 



** Mantle open, no siphonal tubes or sessile. 

 MYTILIDJE Mytilus. 



Dreissena. 



Modiola. 



Crenella. 



Pinna. 



Avicula. 

 UNIONID^E Unio. 



Anodon. 



*** Mantle open, tubes sessile or short. 

 ARCADE Area. 



Pectunculus. 



Nucula. 



Leda. 



Galeomma. 



Lepton. 



