THE NATURAL HISTORY SURVEY. 217 



very small; jaw provided with an accessory plate; lingual 

 membrane with a high, narrow, central tooth, tricuspid; lat- 

 erals of same size, bi- or tricuspid; margins with narrow bases, 

 multicuspid. 



GENUS SUCCINEA Draparnaud, 1801. 



Shell: Very thin and fragile, imperforate, ovate; aperture 

 very large, occupying the greater part of the shell; columella 

 acute, simple; peristome straight, simple. 



Animal: Elongated, truncated before, pointed behind; 



Fig. 54. 

 Animal of SUCCINEA OVALIS Say. (Original.) 



mantle protected by a shell, but not concealing the entire 

 animal as in Helix; respiratory and anal orifices on right of 

 mantle edge, just beneath the peristome; generative orifice be- 

 hind right eye-peduncle; caudal mucus pore absent; locomo- 

 tive disk (?) (Fig. 54). 



Jaw: Arched, with large, quadrangular accessory plate; 

 the ends (of jaw) acuminate or blunt; cutting edge with median 

 projection, frequently broken by ends of ribs. Lingual mem- 

 brane resembling that of Patula. The middle portion of the 

 lower edge of the base of attachment of the central tooth is 

 peculiarly cut away and thinned, as is also the inner lower 

 lateral angle of the base of the laterals and marginals. The 

 marginals are peculiarly constructed as regards the cusps, 

 there being two small outer side cusps, each bearing cutting 

 points; the reflection is quite small when compared to the size 

 of the base of attachment. 



Genitalia: Mr. W. G. Binney thus describes the genitalia 

 (of 5. ovalis): "The testicle is not separated into distinct fas- 

 ciculi by the parenchyma of the liver, as in Helix, but forms a 

 single mass; the epididymis is very much convoluted, and ap- 

 pears always to be distended with spermatic matter; the pros- 

 tate gland is usually short, occupying the upper half only of 

 the length of the oviduct, and is thick, clavate, and more or 

 less covered by pigmentum nigrum cells upon the surface; the 

 penis sac is long, cylindroid, curved downward at its upper 



