462 auriculid^. 



Family AURICULID^. 



Lingual membrane broad and elongated ; teeth numerous, in 

 slightly bent, cross series ; central tooth equilateral ; lateral teeth 

 rather inequilateral, dhninishing in size towards the outer edge. 

 Head ending in a snout ; mouth with a horny lunate upper jaw, 

 and with two dilated buccal lobes, united above, separated below ; 

 tentacles sub-cylindrical, contractile ; eyes sessile at the inner sides 

 of the bases. Mantle closed, with a thickened margin ; foot long, 

 posteriorly blunt ; respiratory orifice posterior, on the right side, 

 excretory orifice near it. Sexes united, orifices of generative or- 

 gans distant, on tlie right side. 



Shell si)iral, covered with a horny epidermis ; aperture elongate, 

 with strong folds on the inner lip ; outer lip often dentate. 



Animal usually frequenting salt marshes. 



The AuricvlidcB are easily distinguished from the other inopercu- 

 lated air-breathing Mollusks. Tliey are furnished with but one pair 

 of non-retractile tentacles, on the inner base of which are situated 

 the sessile eyes. The head is extended beyond the tentacles into 

 an obtuse, rounded, bilobed snout. The mantle is thin, thickened 

 on its margin. The foot is elongated and pointed. The sexes are 

 united in each individual. 



The shell is spiral, extremely variable, and in the American spe- 

 cies conic, generally with a flattened spire, and furnished with nu- 

 merous tooth-like laminae, which contract the narrow aperture. The 

 internal septa are usually removed. 



The Anriculidce are amphiljious Mollusks, breathing free air, Ijut 

 apparently dependent for existence on a great deal of moisture, if 

 not on tlie actual vicinity of the sea. Some species pass their whole 

 life under circumstances which seem to preclude the possibility of 

 their respiring air. Thus Alexia myosotis is often found on isolated 

 stones in salt marshes, which are entirely covered by the tide four 

 hours out of twelve. Tiiis species, when immersed in fresh water, 

 becomes benumbed and soon dies. 



CarycMum exig-uum, on the other hand, though found under sim- 

 ilar circumstances, does not depend on tlie proximity to salt water, 

 being widely distributed far beyond its influence over the interior 

 of the country. Blaimeria pellucida, also, has been detected living 



