SUCCINEA. 



415 



The general arrangement of the lingual membrane is as in Patula. The 

 characters of the separate teeth are seen in PI. X. Fig. K. The peculiar char- 

 acter of the dentition is the cutting away or thinning of the middle portion of 

 the lower edge of the base of attachment in the central teeth, and the inner 

 lower lateral angle of the base of attachment in the laterals and still more in 



Fig. 292. Fig. 293. 



Jaw of S. Totlcniana (Morse). 



Jaw of S. avara. 



the marginals. The marginal teeth are also often peculiar in the denticulation 

 of their reflected cusps. They have usually two small outer side cusps, the 

 inner the smaller, each bearing cutting points proportioned to their size. The 

 reflection of the teeth is also small in proportion to the base of attachment. 

 In other respects the dentition of the genus is very much like that of the 

 Helicece. 



The genital system in the species examined by me presents one peculiarity 

 which may prove a generic character; the testicle is not separated into distinct 

 fasciculi by the parenchyma of the liver, but forms a single mass. The pros- 

 tate gland, also, is very much swollen, and extends only about the half of the 

 length of the oviduct. 



Fig. 294. 



Succinea Haydeni, W. G. Binney. 



Shell elongate-oval, thin, shining, amber-colored; spire short, acute; whorls 

 3, convex, the last marked with the wrinkles of growth, 

 and irregular, heavy, spiral furrows ; suture moderate ; 

 columella covered lightly with callus, and allowing all 

 the interior whorls to be seen from below to the apex ; 

 aperture oblique, oval, five sevenths the length of the 

 shell, the lower portion of its margin considerably ex- 

 panded. Length, 21 mill. ; diameter, 9 mill. 



S. Haydeni. Succinea Haydeni, "W. G. Binney, Proc. Acad. Nat. Sci. 



Phila., X. 114 (May, 1853); Terr. Moll., IV. 40, PI. 



LXXIX. Fig. 1. — Pfeiffee, Mai. Blatt., 1859, 52. — Bland, Ann. N. Y. 



Lye, VIII. 168, Fig. 14 (1865). — Tiiyon, Am. Journ. Conch., II. 236 (1866). 



— W. G. Binney, L. k Fr.-W. Sh., I. 256 (I860). 



A species of the Northern and Interior Regions. Nebraska, between the 

 rivers Loup Fork and L'Eau qui Court. 



