CHAPTER III 
THE GASTROPODA 
CLASS II.—GASTROPODA, CUVIER 
(= PARACEPHALOPHORA, Blainville ; ANISOPLEURA, Lankester). 
Susp-Ciass J. STREPTONEURA. 
Order 1. Aspidobranchia. 
Sub-Order 1. Docoglossa. /~ < 
i 2. Rhipidoglossa. 
Order 2. Pectinibranchia, 
Sub-Order 1. Taenioglossa. / © 
, 
a 2. Stenoglossa. / 6 < 
Sus-CLass II. Eurayneura. /€ 
Order 1. Opisthobranchia, 
Sub-Order 1. Tectibranchia. 
ps 2. Nudibranchia. / 74 
Order 2. Pulmonata. /* / 
Sub-Order 1. Basommatophora. 
a 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 with 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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