Ohio Shells. 375 



practical remarks upon me shells whose structure they have 

 studied in their native beds, have a somewhat satirical cast. We 

 hope these practical remarks will be continued; they will prove 

 an admirable corrective to that fault of extensive generalization 

 from slender premises, which inexperienced and ardent persons 

 are apt to fall into. Our readers, perhaps, understand that the 

 characters which some writers on these shells have resorted to, 

 upon which to found their species, are derived from their shape, 

 and the external marks which they bear. Thus the imio plkalus 

 is so called from having inequalities on the shell, which are called 

 folds; the uriio sulcatus, from its having indents or furrows; the 

 unio cornutus, from protuberances, which are called horns ; the 

 unio verrucosus, from protuberances, thought to resemble warts; 

 the unio tuherculatus, from protuberances resembling tubercles ; 

 the unio securis, from a resemblance to the edge of an axe : then 

 there is the imio circulus, unio orbiculalus, unio subrotundus, unio 

 triangularis, from their approximation to a round or angular 

 shape. It is usual to find the unios of the Ohio, very much de- 

 corticated at the beaks ; one, from being particularly so, has been 

 called u7iio cariosus, or the carious unio. 



Messrs. Short and Eaton lay the axe at the root of all these 

 hasty attempts at classification, by showing that the carious unio 

 of the Ohio, is also found in the Miami, where it is not in the least 

 degree carious ; and that some of these shells are nearly circular, 

 some quadrangular, some ovate, and some almost perfectly elipti- 

 cal, so that here we have a unio which is without its own specific 

 characters, whilst it has got those of almost every other shell ; for 

 it has got its place in the books as u7iio cariosus, whilst it is never 

 carious in the Miami, and has the distinctive cognominal charac- 

 ters of the unio ellipsis, the unio circulus, the unio orbiculatus, the 

 unio subrotundus, the unio ovatus, &c. &c. &c. 



Thus we see how insecure are the grounds upon which men 

 build, who trust to the external forms of shells, as the sole means of 

 giving to an important family of molluscous animals their proper 

 place in the scale of animal existences. These animals could not 

 pursue the same object with less effect, if it were given to them 

 to attempt to assign a natural place to our biped race, by de- 

 scribing all the dwelling houses between the Delaware and 

 Schuylkill, where some are amorphous from want of taste, some 

 mean from the poverty of the owner, others ornamented and 



