DIPLODON 1289 



abdoiT>inal sac ; outer g-ills pointed below in the middle ; palpi 

 triangular ; branchial opening papillose ; anal opening smooth, 

 not separated from the superanal opening. 

 I^P^' U^iio aiistralis Lamarck. 



Section Hyridrlla s. s. 



Shell covered with concentric, sulcate sculpture ; pseudocar- 

 dinals well developed, compressed ; laterals delicate, sometimes 

 imperfect. 



Group of Diplodon dorsuosus. 



Shell somewhat rhomboid, inflated solid, with rather full 

 beaks, the sculpture consisting of very strong, subradial, cor- 

 rugated ridges, which curve toward each other below, those 

 in the center sometimes joining, this sculpture extending well 

 out on the disk ; upper part of posterior slope having slight 

 radial folds. 



DiPi^oDON ix>RSUosus (Gould). 



Shell oblong, subrhomboid, convex or subinflated, subsolid, 

 inequilateral ; beaks but slightly elevated, their sculpture coarse 

 and strong, consisting of subradial, corrugated or nodulous 

 bars, which curve towards each other ; this sculpture extends 

 out on to the disk and becomes very irregular ; anterior end 

 slightly narrowed and rounded ; posterior end almost squarely 

 subtruncated ; posterior ridge full and rounded ; dorsal line 

 lightly arched ; base line straight ; surface with faint, irregu- 

 lar, concentric sculpture and traces of radial grooves ; the mid- 

 dle of the disk is often faintly pustulous ; epidermis almost 

 black, shining ; pseudocardinals compressed, more or less dou- 

 ble in each valve ; laterals remote, short ; nacre bluish, much 

 thicker in front. 



Length 59, height 35, diam. 22 mm. 



Length 59, height 33, diam. 19 mm. 



Nepean River, Australia. 

 Unio dorsuosus Goui.d. Pr. Bost. Soc. N. LL, IH, 1850, p. 296; 



V. S. Expl. Exp., Xn, 1852, p. 430, figs. 540, 540a, 540&. 

 Marg,aron (Unto) dorsuosus Lka, Syn., 1852, p. 21. 

 Diplodon dorsuosus Simpson, Syn.. 1900, p. 889. 



