24 DONAX. VENUS. 



the anterior slope very obtuse ; hinge with two 

 cardinal teeth, and one lateral tooth. 



'' The most striking characteristic of Donaoj 

 is the broad, thick extremity of one end, gradually 

 lessening towards the other. A rich purple tint 

 is very frequent in tiiese shells. Dona.v denticu- 

 latus and triinculus are common British exam- 

 ples. (Plate 4.) You must remark the liga- 

 ment of Dona.v, which is exterior. 



^' Our next genus ranks highest for beauty 

 among the bivalves, and takes its name from the 

 goddess Venus. The species amount to one 

 hundred and sixteen in the Linnoean system, but 

 other authors have formed several new genera. 



" Shell bivalve, having the lips incumbent on 

 the anterior margin ; hinge with three teeth, all 

 approximate, the lateral ones diverging at the lip. 



" I am afraid," said Lucy, " that we shall find 

 this genus Very difficult : I wish you would tell us 

 the new genera that have been formed out of it.'' 



" Learn first to know the general appearance 

 of Vefiiis, and remark especially the teeth. You 

 may also bear in mind that the beaks are almost 

 always turned to the posterior slope, and from 

 the ligament. The area and areola are also very 

 conspicuous : the area is generally large, and dif- 

 ferently coloured to the disk. Venus Papkia is 

 pretty .(Plate 4.) The spinous species, V. Dlone, 

 is more beautiful, and is the only shell of the 



