ANCYLUS. 219 



vegetable matters. They are timid, rarely change 

 their places, walk very slowly, and do not swim. 

 The eggs are ovoid, hyaline, four or eight, placed 

 in a row in a horny, mucous, orbicular, depressed, 

 transparent capsule attached to solid bodies. 



Teeth (30, 1, 30) central, much compressed, apex 

 with a single sharp point; lateral teeth bent and 

 hooked, the first simple, the last contracted at the 

 bend and denticulated. (Figured by Otto Goldfuss, 

 49. t. 7. f. n.; and Weigmann, Arch. 1836, t. 10. f. 

 911.) 



It is no proof that the animals do not breathe free 

 air because they are usually observed attached to 

 stones, like Patella, at the bottom of the water ; for 

 Limnaus pereger is more frequently found at the 

 bottom of the water on the mud than in any other 

 place, and I have seen a specimen in exactly the 

 same place for several days without moving. But 

 the Ancyli are often found, as has been observed by 

 Mr. Jeffreys, out of the water, and only within reach 

 of the spray of a waterfall. 



98. 1. ANCYLUS Jluviatilis. Common River Lim- 

 pet. Shell conoid, with the point recurved 

 and near one end; aperture roundish-oval, 

 disk bluish. 



Ancylus fluviatilis. Miiller, Verm. ii. 201.; Drap. Hist. p. 48. 

 t. 2. f. 23, 24.; Brard, p. 200. t. 7. f. 3.; Sowerby, Gen. 

 fig. 1.; Turton, Man. ed. 1. t. 140. f. 125.; Forbes and Han- 

 ley, B. M. iv. 186. t. 122. f. 4. ; Clark, Ann. and Mag. N. H. 

 xv. 278. Patella fluviatilis. Lister; Da Costa, B. C. i. 

 t. 2. f. 8.; Mont. p. 482. Patella lacustris. Linn. S. N. 

 1260.; Turt. Diet. p. 138. Crepidula lacustris. Fleming, 

 Ency. Ancylus simplex; A. Janii; A. gibbosus; A. cyclo- 



