CHAPTER III 



THE GASTROPODA 



CLASS II. GASTROPODA, CUVIER 

 ( = PARACEPHALOPHORA, Blainville } ANISOPLEURA, Lankester). 



SUB-CLASS I. STREPTONEURA. 

 Order 1. Aspidobranchia. 



Sub-Order 1. Docoglossa. 

 2. Rhipidoglossa. 



Order 2. Pectinibranchia. 



Sub-Order 1. Taenioglossa. 

 ,, 2. Stenoglossa. 



SUB-CLASS II. EUTHYNEURA. 

 Order 1. Opisthobranchia. 



Sub-Order 1. Tectibranchia. 

 2. Nudibranchia. 



Order 2. Pulmonata. 



Sub-Order 1. Basommatophora. 

 2. Stylommatophora. 



Definition. The Gastropoda, together with the Scaphopoda and 

 the Lamellibranchia, form the branch Prorhipidoglossomorpha of 

 the Mollusca, that is to say, a group in which the gonads are no 

 longer in direct communication Avith the pericardium, the foot is 

 wholly posterior to the head, and a visceral commissure is present. 

 The Gastropods are a class of the Prorhipidoglossomorpha specially 

 characterised, firstly, by their asymmetrical organisation ; secondly, 

 by their well-developed head ; and thirdly, by their shell, which is 

 formed of one piece and coiled in a spiral, at least in the larval 

 stage. 



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