DIPI.ODON 1305 



in front ; beaks probably not much elevated or inflated ; pos- 

 terior ridge full, rounded ; anterior end rounded, cut away a 

 little below ; base line nearly straight ; posterior end obliquely 

 truncate above, rounded below ; surface with uneven, concen- 

 tric sculpture, the hinder two-thirds covered with irregular 

 pustules, which are strongest on the posterior part of the 

 shell : sometimes they are arranged in broken ridges ; epider- 

 mis brownish or blackish ; left valve with two small, stumpy 

 pseudocardinals and two remote, faint laterals ; right valve 

 with two pseudocardinals, the upper very small, and one re- 

 mote lateral ; dorsal scars few, well exposed in the shallow 

 beak cavities : adductor scars shallow, the small ones imme- 

 diately under the pseudocardinals, deep ; pallial line crenated ; 

 nacre dirty l)luish, often lurid purple in the cavities, much 

 thicker on the anterior base. 



Length T32. height 50, diam. 32 mm. 



Australia. 

 Unio novcr-hoUandia: Gray, Pr. Zool. Soc. Lond., 1834, p. 57. 

 Margarita (Unio) noi'cr-hollandice Lea. Syn., 1836, p. 17; 1838, 



p. 16. 

 Margaron (Unio) novff -holt an dice Lea. Syn.. 1852, p. 23; 1870, 



P- 3.S- 



Diplodon noicr-hollandia' Simpson, Syn.. icxx), p. 893. 



Unio cncmnoides Lea, Proc. Am. Phil. Soc, 1840, p. 285 ; Tr, 

 Am. Phil. Soc, VITL 1842, p. 192, pi. vii, fig. 2; Obs., IIL 

 1842, p. 30. pi. vii, fig. 2.— Hani.ey, Biv. Shells, Sup., 1856, 

 p. 382, pi. XXIV, fig. 4. — Chenu, 111. Conch., 1858, pi. xxvii, 

 figs. 3, 3a, 3&. — KusTER, Conch. Cab. Unio, 1861, p. 219, 

 pi. i,xxiv, fig. I. — Reeve, Conch. Icon., XVI, 1865, pi. xix, 

 fig. 89. 



Margaron (Unio) cucuinoides Lea, Syn., 1852, p. 21 ; 1870, 



P- 31- 

 f Unio cumingianns Dunker, Zeits. fiir Mai., 1853, p. 53. 



A striking species, which dififers from D. ivchstcri in being 

 more elongated, narrower in proportion in front, in having a 

 higher posterior ridge, along which lies its greatest diameter, 

 and in having the anterior two-fifths of the shell nearly free 



