36 



LAND AND FRESH- WATER SHELLS OF N. A. [TART L 



Fig. 45. 



A variety with an open umbilicus is sometimes found (Fig. 45), 

 Jaw somewhat arcuate, long, narrow, ends somewhat 

 attenuated, pointed ; anterior surface with central longi- 

 tudinal strifE ; concave margin smooth, with a slightly 

 developed, broad median projection. 



Lingual membrane very 

 broad, with 53 rows of 79 

 teeth each (39—1—39) ; cen- 

 trals tricuspid, the median 

 cusp very large and longer 

 than the plate on which it 

 rests ; laterals three only on each side, bicuspid, arranged in a 

 straight transverse row ; uncini pointed, curved, thorn-shaped, 



Fig. 47. 



Fig. 46. 



Jaw of Hyalina indentata. 



[MOKSE.] 



Lingual dentitioa of Hyalina indentata. [Morse.] 



greatly diminishing in size as they pass off laterally, arranged in a 

 slightly crescent-shaped row on each side of the lingual membrane. 



Fig. 48. 



Hyalina limatuln, Ward. — Shell widely umbili- 

 cated, small, depressed, thin ; epidermis whitish, immacu- 

 late ; suture distinctly imjjressed ; whirls more than four, 

 convex, with very fine, oblique, parallel striae, which become 

 obsolete on the base ; aperture oblique, subcircular, slightly 

 modified by the penultimate whirl ; peristome thin, acute, 

 its ends approaching ; umbilicus rounded, large and deep, 

 not exhibiting all the volutions. Greater diam. Sj, lesser 

 5 ; height ^ mill. 



Eelix limatula, Wakd, MSS. in Binney, Bost. Journ. Nat. 



