348 



SUBKIN6D0M MOLLUSCA. 



Helicidae (spiral-form).— The Land-snail has four tenta- 

 cles, the longer pair with eyes at the extremity. It lays its 

 eggs singly, while the other Orders lay theirs in chains.* 



Limacidae. — The Slugs are snails without the shell, or 

 with only a rudimentary one coucealed in the mantle. 



ORDER OPISTHOBRANCHIATA. 



General Characteristics. — The Opisthobranchs (gills 

 behind) are geaerally naked, with feathery gills behind the 



heart. 



Fig. lae. 



^E6lis^ Britain. 



The toll's is typical of the order, having its gills arranged 

 in tufts along the back, and the tentacles non-retractile. 



ORDER NUCLEOBRANCHIATA. 

 General Characteristics. — The Nucleobranchs (clus- 



Carinaria medlierranla. 



* If placed upon a pane of i^lase, by looking underneath, one can easily obserre 

 JtB curiouB profession by means of a single foot. 



