332 On the Teeth of the Pneumonobranchiate Mollusca. 



lingual membrane is broad ; the teeth numerous, similar, uni- 

 form, in numerous straight cross series on each side of a narrow 

 central equilateral tooth ; the lateral teeth are very nearly equi- 

 lateral, with a broad, flat, subcentral, subequilateral tip. 



Onchidiad^. 



The teeth of a new species of Onchidium, very like O. Cel- 

 ticum, from the coast of West Africa, are very similar to those of 

 Helix, with a short and narrow central tooth in each cross series : 

 the foot of this animal, when preserved in spirits, is quite mar- 

 gined by the mantle and folded across by deep grooves into 

 divisions ; the tentacles are completely retractile. 



Peroniad^. 



The teeth of Peronia Mauritiana are so like those of Testacelhis, 

 that the description and figure of them will almost suit for these 

 (see fig. 1). 



AURICULID^. 

 Fig. 3. Auricula. 



The teeth of Auricula (fig. 3) are very like those of Bulimus. 

 The lingual membrane is broad, elongated ; the teeth numerous, 

 in a slightly bent cross series on each side of an equilateral nar- 

 row central tooth; the lateral teeth are rather inequilateral, 

 diminishing in size towards the other edge. 



Lymnead^e. 



The teeth of Lymnea, Planorbis, Physa and Ancylus are ex- 

 tremely similar, and have been well described by Dr. Troschel 

 and Mr. Thompson. 



Amphibolid^. 



Fig. 4. Amphibola. 



The teeth of Amphibola nux avellana (fig. 4) are very similar to 

 those of Lymnea. The lingual membrane is large, very broad, 

 expanded and long, with a central space or line scarcely defined ; 

 the teeth are numerous, equal, similar, four-sided, rather longer 



