MULTIVALVES AND BIVALVES. 43 



brief one of the systematic schemes that has much to recommend it, 

 mentioning only such families as are represented in the British 

 fauna so far as at present known. 



I. CEPHALOPODA. 



i. Dibranchiata. 



1. Octopoda. 



Octopodidae. 



2. Decapoda. 



1. Phragmophora. 



Spiruhdae (drifted specimens only). 



2. Se<piophora. 



Sepiidae. 



3. Chondrophora. 



Sepiolidas. 



Loliginidae. 



Ommastrephidse. 



ii. Tetrabranchiata (none). 



II. GASTROPODA, 

 i. Amphineura. 



1. Polyplacophora. 



Lophyroidea. 



2. Aplacophora (none). 



ii. Prosobranchiata. 



1. Diotocardia. 



1. Docoglossa. 



Acmasidae. 

 Lepetidse. 

 Patellidae. 



2. Rhipidoglossa. 



Zygobranchiata. 



Fissurellidae. 



Haliotidae. 



Plejirotomariidae, 

 Azygobranchiata. 



Cyclostrematidae. 



Trochidas. 



Turbinidae. 



Neritidae. 



2. Monotocardia. 



i. Ptenoglossa. 

 lanthinidae. 

 Scalariidse. 



