VENUS. 



The V, Gnidia, F. Dombeyi, and others form a fifth 

 division ; in one valve of these the posterior tooth is very 

 large and thick, and the two anterior teeth small and 

 placed near together, having just space enough to receive 

 the thin lamellar anterior tooth of the left valve between 

 them; in the left valve the middle tooth is thick and 

 double, and the posterior is elongated and narrow ; these 

 are slightly lamellose, muricated or cancellated exter- 

 nally, and the siphonal impression is rather large and 

 acuminated. 



In all the above five divisions the lunuJe or heart 

 shaped impression seen just below the beaks when the 

 valves are closed is distinctly circumscribed by an im- 

 pressed line. In the following this is not so. 



We may next particularize those species which are 

 nearly orbicular in form, with three diverging teeth in the 

 hinge, a large pallial sinus acute at its anterior end, and 

 a flat space immediately below the fulcrum to which the 

 ligament is attached ; the V. Chinensis may be regarded 

 as the principal species of this division. The exterior 

 surface of these is nearly smooth. 



The following are the principal characters of some 

 shells which may form a seventh division, viz., in the 

 right valve the two anterior teeth are thin and lamellar 

 and placed near together, receiving between them a simi- 

 lar anterior tooth of the other valve, and the posterior 

 tooth is thin, lengthened and double; in the left valve 

 the middle tooth is thick and large, and the posterior tooth 

 very thin and linear : the shells of this division are of an 

 ovate form and very thin, and the siphonal impression is 

 large : we have represented one of them at fig. 9. 



The eighth and last division may consist of such 

 shells as are smooth outside, with a small rounded sinus 

 in the pallial impression, in these there are three large 

 and distinct teeth in the left valve ; there are also three 

 teeth in the right valve, the anterior tooth is however very 

 small in this valve ; these are a near approximation in 

 appearance to many Cythereae. 



The Veneres, which are very numerous, are found in 

 the sand and gravel of the floor of the sea, and they 

 appear to belong to all countries and climates ; we have 



