Baker — A Revision of the Limnaeas of Northern Illinois. 7 



iDg ; spire sharply conical ; sutures very deeply indented ; 

 aperture elongately-ovate, somewhat expanded; peristome 

 thin, acute; columella thickened by a testaceous deposit, and 

 bearing a heavy plait across the middle; the columella is re- 

 flected at the lower end, the reflection almost covering the 

 umbilicus, which is narrowly open ; the umbilical region is 

 somewhat indented. The surface is sometimes broken up by 

 coarse, spiral semi-ridges, with facets forming a somewhat 

 reticulated surface. 



Length 12.00; width 6.00; aperture length 6.00; width 3.00 mill. (8457.) 



« '<■ 6.00; " 3.50 " (8457.) 



< " 5.50; <c 2.50 " (8457.) 



» " 4.50; " 2.50 " (8457.) 



'« " 7.50; «« 4.00 " (8468.) 



Animal (f. 3, after Binney) : With a very small, more or 

 less oblong foot, when viewed from the base, the anterior and 

 posterior borders rounded ; color dark gray 

 or blackish, lighter below ; the whole surface 

 is dotted with whitish, which is specially 

 noticeable about the eyes; tentacles trian- 

 gular, flat, short, more or less transparent; 

 the black eyes are placed on prominences at 

 the inner base of the tentacles ; respiratory fig. 3. Animal of 

 orifice on the right side, near the angle of Limnaea desidio- 

 the peristome and body whorl. Length of *"***• < BiQIie y. 

 foot 5.00, width 3.00 mill. The heart is 

 situated near the umbilicus and the pulsations are very rapid ; 

 the writer counted 150 to 155 per minute. 



Jaw: As usual. 



Radula formula: f-^ + f + 1 + \ + i + 1 •+ f£ (46 — 1 

 — 46): central tooth as usual; lateral teeth with a subquad- 

 rate base of attachment, the reflection very broad, bicuspid, 

 the inner cusp long, reaching below the lower margin of the 

 ba^e of attachment, the side cusps smaller; the 8 to 16 laterals 

 are tricuspid, the inner cusp very small; these may be called 

 intermediate marginals; marginals at first (17 to 20) modified 

 laterals, with a long, bifid inner cusp and two very short outer 

 cusps ; rest of marginals long and narrow, serrated, gen- 

 erally three short cusps at the distal end and two short cusps 



