1222 PRISODON 



Diplodon furcatuni Spix, Test. Fluv., Bras., 1827, p. 35, i>l 



XXVII, figs. I, 2. 

 Hyria clongata Swainson, Ex. Conch., 1841, p. 29, pi. xxiv. 

 Triquetra elongata H. and A. Adams, Gen. Rec. Moll., II, 1857, 



p. 508. 



This species is considerably elongated ; the post-basal point 

 is elevated to some distance above the base line; the base is 

 somewhat rounded. In young shells the posterior wing is 

 often greatly produced and elevated and the outline of the 

 dorsal slope is much incurved, but in old specimens the wing is 

 low and worn away behind. 



Prisodon RECTUS (Sowerby). 



Shell elongated, solid, strongly winged before and behind, 

 inequilateral; beaks full and somewhat elevated; posterior ridge 

 semi-double, elevated, ending behind in a faint biangulation at 

 the base of the shell ; dorsal outline curved upward ; anterior 

 and posterior wings extended; outline of dorsal slope greatly 

 incurved above; outline of anterior end incurved under the 

 wing, rounded and cut away below ; base line nearly straight ; 

 surface irregularly, concentrically striate ; epidermis chestiuit- 

 colored. 



Length 130, height 53 mm. 



South America ; locality unknown. 

 Hyria recta Sowerby, Conch. Icon., XVII, 1868, pi. v. fig. 10. 

 Prisodon rectus Simpson, Syn., 1900, p. 871. 



An elongated, almost rhomboid form with considerably pro- 

 duced wings ; the dorsal and basal outlines being nearly straight 

 and parallel. The posterior ridge seems to be elevated above 

 the rest of the shell. 



Prisodon brownianus (Lea). 



Shell rather small, elongated, subrhoiuboid, inflated, sub- 

 solid to solid, inequilateral ; beaks full and high ; posterior 

 ridge strong, narrowly rounded, ending in a blunt point at 

 the base of the shell ; dorsal line nearly straight, scarcely 

 winged before or behind ; surface with strong, concentric 

 growth lines and traces of radial sculpture, greenish-brown. 



