378 BLUE ACANTHURUS. 



Acanthurus, and the genus Teuthis is, in conse- 

 quence, annulled. The blue Acanthurus is a native 

 of the Indian and American seas, and is said to 

 arrive at the length of ten or twelve inches, or even 

 more, though the specimens usually seen are con- 

 siderably smaller : in shape it resembles the major 

 part of the Chaetodons, the head sloping in front 

 from the origin of the dorsal fin : the colour, in 

 the recent fish, is a deep or blackish blue, which in 

 specimens preserved in spirits of wine, usually fades 

 into a ferruginous brown : on each side the body 

 is a very large, oblong-ovate whitish patch or spot, 

 surrounded by a border of a deeper cast : the skin 

 is roughened by very small scales : the tail is 

 slightly lunated, dusky on the upper and lower 

 part, and marked towards the base by a whitish 

 ovate spot : the teeth are crenated, and on each 

 side the base of the tail, is a very strong spine, 

 which, as in most others of the present genus, is 

 erigible at the pleasure of the animal, in an hori- 

 zontal direction, from the channel in which it lies. 

 The fish figured by Catesby in his Natural 

 History of Carolina, under the name of the Tang*, 

 is generally considered as representing the present 

 species : yet, if Catesby's description be accurate, 

 the Tang is destitute of teeth; and, from the figure 

 accompanying the description, appears to want the 

 ventral fins, is covered with middle-sized scales, 

 and is entirely of a deep blue colour without any 

 variegation. As Catesby however was not remark- 



* Turdus rhomboidalis. Catesb. Car. 2. t. 10. 



