155 



DORAS. 



Valenciennes divides his genus into two forms : 

 those having the mouth cleft at the extremity and 

 furnished w^ith teeth on each jaw, and those hav- 

 ing it placed below with teeth in groups on the 

 lower jaw only. The characters given by Spix ap- 

 ply more particularly to the large species described 

 as Corydoras edentatus, Spix, Doras Humholdtii^ 

 Agassiz, the J), niger of the present volume ; we 

 would consider that which we are about to de- 

 scribe as more typical, where the plates cover the 

 whole body with the exception of the belly and the 

 centre of the back. The " corpus nudum" must 

 therefore be taken under modification, so also must 

 the " OS parvum" which is sometimes of consider- 

 able size and cleft terminally. The characters in 

 Spix are : — 



" Deutes velutini, minuti, in mandibula, ossibus inter-maxil- 

 laribus imoque in vomere. Membrana branchiostega radiis sex. 

 Os 'parvum. (Os mediocre terminalis inferiusve). Cirrhi sex. 

 Caput clj^eatum. Corpus nudum (omit ' corpus nudum ') in 

 utroque (vero), corporis latere series scutorum osseorum, in me- 

 dio spina aut carina elevata instructorum. Pinnse dorsales duae, 

 posterior adiposa, interdum vix distincta. Radius primus pin- 

 narum pectoralium, et pinnse dorsalis validissimus, serratus." 



In the first division, and tyi^ical of what we shall 

 consider the true form of Doras, we possess speci- 

 mens and drawings of three species. The first agrees 

 closely with the minute description of D. costatus 

 which is given by Valenciennes, and to this we 

 * Probably from ^o^m, a spear. 



