Din.ODON 1275 



young, granular, vertically striate and breaking into denticles 

 in the old shell ; laterals long, curved, granular, often verti- 

 cally striate ; anterior scars smooth, distinct. 



DiPLODON I'ARAI^LELIFIPEDON (Lea). 



Shell greatly elongated, subrhomboid, rather solid, inflated, 

 very inequilateral ; beaks full and somewhat elevated above the 

 dorsal line, their sculpture a iew, strong, short, radial bars ; 

 posterior ridge high, angled on the earlier growth, ending be- 

 hind in a point near the base line ; surface having irregular, 

 concentric sculpture; epidermis bright, dark bottle-green with 

 narrow, concentric bands of light green ; left valve with two 

 pseudocardinals, the anterior high, rough and subcompressed, 

 the hinder low, with two straight, granular laterals ; right valve 

 with two compressed pseudocardinals, the vipper small, and one 

 lateral having a vestigial one at its base; all the teeth showing 

 indications of vertical striation ; anterior scars deep ; posterior 

 scars impressed ; nacre silvery-white, a little thicker in front. 



Length 85, height 32, diam. 27 mm. 



Rio de la Plata system. 

 Unio parallelipipedon Lea, Tr. Am. Phil. Soc, V, 1834, p. 60, 



pi. VIII, fig. 20 ; Obs., I, 1834, p. 172, pi. VIII, fig. 20. — Kus- 



TER, Conch. Cab. Unio, 1861, p. 220, pi. lxxiv, fig. 2. — Sow- 



ERBY, Conch. Icon., XVL 1868, pi. lxxxix, fig. 478. 

 Margarita (Unio) parallelipipedon Lea. Syn., 1836, p. 35; 



1838, p. 24. 

 Margaron (Unio) parallelipipedon Lea, Syn., 1852, p. 36; 



1870. p. 58. 

 Diplodon parallelipipedon Simpson, Syn., 1900, p. 884. 

 Unio bonplandi Valenciennes, Continuation of Humboldt's 



Zool. Obs., 1827. 



A striking, elongated species, which is remarkable for the 

 wide, bottle-green belts alternating with narrower ones of 

 lighter color. 



Dtpeodon patagonicus (d'Orbigny). 



Shell oblong, subrhomboid, rather solid, very inequilateral, 

 subinflated, with' a strong, rounded posterior ridge, which 

 curves up a little in the middle and ends behind in a rounded 



