392 THE OCEAN WORLD. 



The third is ^Eolidse, types Glaucus and 



The fourth is Tritoniadse, types Scyllaea and Tritonia. 



The fifth is Doridse, types Idalia and Doris, the curious sea-lemon. 



The first family of the second division, Tectibranchiata, is Phyl- 

 lidiadse, types Diphyllidia and Phyllidia. 



The second family is Pleurobranchidse, types, Umbrella, in form 

 resembling a limpet, and Pleurobranchus. 



The third family is Aplysiadse, types, Dolabella and Aplysia. 



The fourth family is Bullidse, types, Scaphander, Acera, and Bulla. 



The fifth family is Tornatellidse, types, Tornatina and Tornatella. 



The third order is the Pulmonifera, and the fourth is the Prosobran- 

 chiata ; we shall speak of them in the next chapter. 



In this family we reach a group of Gasteropods much more 

 numerous, both in species and in special types, which respire by the 

 aid of branchiae, or gills. Cuvier divides them into many orders, 

 based chiefly upon their respiratory organs. 



The Tectibranchiata have the gills attached either to the right side 

 of the body or upon the back, arranged in the form of leaflets, more 

 or less divided, but not symmetrical, and nearly covered by the mantle. 

 Bulla and Aplysia are the two principal genera of the group, and 

 may be considered as the type of two small families. 



The Aplysise were known to the ancients under the name of sea- 

 hares (Lepus marinus), from some fancied resemblance to the terres- 

 trial hare. They were objects of profound horror, inspired either by 

 their singular form, or from an acrid, caustic, and inodorous liquid 

 which they secrete. A magic influence was attributed to them ; they 

 were supposed, for instance, to have influence over the female heart. 

 It is not easy, however, to explain the evil renown acquired by an 

 animal which is known to be gentle and even timid. They are naked 

 and fat, somewhat resembling the Limnaea in their oval, elongated 

 form, their thickness in the dorsal region, and their posterior locomo- 

 tion. Their head, which is very indistinct, is furnished with four 

 tentacles, the anterior two of which are the largest, and somewhat 

 resemble the ears of a hare. The eyes are found at the base of the 

 posterior tentacles. These characters are observed in Aplysia depilans 

 (Fig. 180). Aplysia inca shows also the same arrangement (Fig. 181). 

 In this family the mollusc is much more important from its volume 

 than from its internal, rudimentary, and horny shell, which is con- 



