THE NATURAL HISTORY SURVEY. 191 



Distribution: Europe and America. 



KEY TO SPECIES OF GASTRODONTA. 



A. Shell depressed, spire almost flat demissa 



B. Shell globular, spire much elevated ligera 



73. Qastrodonta ligera Say, pi. xxviii, fig 14. 



Helix ligera SAY, Journ. Phil. Acad., Vol. H.'p. 157, 1821. 



Helix rafinesquea FERUSSAC, Tab. Syst., p. 50;lHist.[pl. li, a, fig. 5; pi. 



1, a, figs. 4, 5, 1822. 

 Helix wardiana LEA, Trans. Amer.JPhil. Sec., Vol. VI, p. 67, pi. xxiii, 



fig. 82, 1839. 

 G astro donta ligera stonei PILSBRY, The Nautilus.iVol. Ill, p. 46, 1889. 



(Variety.) 



Shell: Umbilicated, orbicular, convex; epidermis shining, 

 straw-colored or yellowish-horn color,[deep yellow on the base 

 of the last whorl, the color frequently running high up toward 

 the suture; whorls seven, covered^with closely crowded, trans- 

 verse striae, which disappear on the base of the shell; umbil- 

 icus small, rounded and deep, appearing to extend clear to 

 the apex of the shell; umbilical region impressed; sutures 

 impressed; aperture rounded, semilunate.'the base and side of 

 the last whorl being covered by a thick, white deposit of tes- 

 taceous matter, greatly thickening that portion of the shell; 



FIG. 41. 

 Animal of GASTRODONTA LIGERA Say."* (Binney, fig. 68.) 



peristome thin, acute; spire elevated, exhibiting nearly all the 

 whorls in a lateral view. 



Gr. diam., 12.00; lesser, 11.00; height/ 9.50; umbil. diam., l.CO mill. (8460.) 

 8.75; " 8.00; " 6.50; " " 0.75 " (8461.) 



Animal (Fig. 41): With a long andjnarrow foot, acutely 

 pointed behind; color slaty-black on the upper surface, lighter 

 on the base and posterior extremity, grayish on the collar; 

 eye-peduncles tapering, slender, rather long, eyes placed as 

 usual; other characters as described for the genus. 



Jaw: Not examined. Said by Binney to be "strongly 

 arcuate, ends rounded; anterior surface striated; concave mar- 

 gin with a well-developed median projection." 



Radula formula: V + +i+ + (38138); centrals 

 tricuspid, the central cusp long, the side cusps short; lateral 

 teeth similar, but bicuspid, the inner cusp the longest; mar- 



