344 Annals of the South African Museum. 



each side and along the straight lower edge with fine hair-like 

 spiuules ; apical claws short and strongly curved, each with a well- 

 marked denticle at the base ; supra-anal angle very slight and occur- 

 ring at a short distance from the base. 



Colour more or less dark yellowish-brown. 



Length of shell reaching 0'48 mm. 



Remarks. This form was recorded as early as the year 1852 by 

 King, and was re-described by the present author in 1888 from speci- 

 mens raised out of dried Australian mud. It is closely allied to 

 D. setigera (Birge), chiefly differing in the want of any distinct sculp- 

 ture of the valves. From the likewise closely allied South American 

 species D. odontoplax it may at once be distinguished by the perfectly 

 smooth edge of the lip-plate. 



Occurrence. This form developed rather abundantly in some of my 

 aquaria prepared with mud from Port Elizabeth. 



Distribution. Australia, Ceylon. 



