DONAX. 



Tlie Donaces are transverse shells, whose two valves 

 are exactly alike; but they are inequilateral, the anterior 

 side, contrary to g"eneral custom, bein^ for the most part 

 the shorter, though in a few species the sides are also 

 nearly equal in length. In one valve there are two, more 

 or less distinct cardinal teeth, and in the other only one^ 

 (for we do not consider the nymphse to which the lig'^ament 

 is attached as connected with the teeth,) hut this one is 

 most commonly divided or notched at its superior ex- 

 tremity.* The lateral teeth are more variable ; in some 

 species, as in D. Scortum, there are not only two distinct 

 lateral teeth, one on each side of the cardinal teeth, and 

 placed near to them; but in one valve there is also a linear 

 posterior process, placed at a distance from the other 

 lateral teeth, and between which and the edge of the shell 

 there is a groove that receives the edge of the other valve 5 

 in other species only the anterior lateral tooth can be dis- 

 tinguished in each valve, and the above mentioned linear 

 process: in other species again, we may observe two 

 distinct lateral teeth in one valve, the posterior being 

 more distant than the anterior, and only the traces of 

 them in the other valve ; and in some the lateral teeth are 

 scarcely distinguishable at all. The ligament is external, 

 generally short, sometimes remarkably so; the principal 

 part of it is anterior, that is affixed to the shorter side of 

 the shell, but in most of the Donaces a small portion of 

 the ligament is also placed behind the umbones. A lai'ge 

 sinus is seen in the impression of the muscle of attachment 

 of the mantle. 



The Donaces are marine, they are most commonly 

 covered with a thin, horny, light coloured epidermis, very 

 few of them are remarkable for the brilliancy or variety 

 of their colours, though some of them are very pretty 

 little shells. The recent species are numerous, and several 

 of them are found on our coasts, of these the D. denticu- 

 lataf is the most remarkable : that named D. Trunculus by 

 English writers is said to be a distinct species by Lamarck, 



* We know that the Donax Meroe as well as tlie D. scripta have two dis- 

 tinct teeth ; but we are not convinced of the propriety of uniting them in the. 

 $'uuie Genus with the other Donaces. 



t The fact of this being a native of our coast wants confirmation* 



