Notes on RaduItE. 



Si 



ARTICLE IX. — NOTES ON RADUL^E. 



By Frank Covins Baker, Chicago, Illinois. 



While preparing a report on the mollusks of the Chicago 

 area, the writer examined the radnlse of many hundred speci- 

 mens, and figured and described many ribbons which were 

 before unknown or but little known. It has been thought 

 best, since the work just mentioned will be delayed some time 

 before publication, that the new radulae, as well as notes upon 

 others already known, be described and figured at the pres- 

 ent time. 



The radulae were all examined from fresh material, not 

 alcoholic, the animals being killed by boiling water. The 

 lingual ribbons were beautifully clear and transparent, and 

 when stained with a 4 per cent solution of iodine the char- 

 acters could be very plainly seen, the cusps standing out in 

 relief against the base of attachment. The objective used gave 

 600 diameters for most of the radulse. The drawings were 

 all made several times, and from several individuals, in order 

 to be sure of each fact. 



While observing the living snails in an aquarium the writer 

 has been impressed by the curious manner in which Lhimcra, 

 Planorbis, P/eurocera, Campelonia, etc., eat; the motion of the 

 tongue is precisely that of a cat lapping milk, although the 

 motion is not quite so rapid as in the latter animal. Land 

 shells, on the contrary, seem to use the jaw for cutting a piece 

 of lettuce (the article of food which the writer uses for snails 

 in captivity), and the ribbon is pressed against the jaw and 

 assists in cutting the lower part of the piece selected. In 

 the fresh - water forms it is the ribbon and not the jaw (or 

 jaws) which collects the food. This, of course, refers only to 

 those species which habitually crawl over the glass sides of 

 an aquarium (or over stones on the bottom) and not to the 

 individuals which eat the leaves of aquatic plants, for they 

 may use their jaws, as do the land snails. 



(Jour. Cin. Soc. Nat. Hist., Vol. XIX, No. 3.) 1 



Printkd Nov. 13, 1897. 



