ACANTHOPTERYGII. 197 



OREOSOMA, Cuvier. 



A small oval fish, whose whole body, above and beneath, is studded with 

 thick cones of a heavy substance. There are four of them on the back, and 

 ten on the belly, arranged in two series, with smaller intermediate ones. It 

 was discovered in the Atlantic, by Peron. 



FAMILY III. 



SCIENOIDES. 



THIS family is closely related to the Percoides, and even presents nearly 

 similar combinations of external characters, particularly in the indentations 

 of the preoperculum, and in the spines of the operculum ; but both vomer and 

 palatines are without teeth; the bones of the cranium and face are generally 

 cavernous, and form a muzzle more or less gibbous. The vertical fins are 

 frequently somewhat scaly. 



Some of the Scienoides have two dorsals, and others have but one; among 

 the former we first find the genus 



Whose common characters consist of a gibbous head, supported by cavernous 

 bones, two dorsals, or one deeply emarginate, whose soft part is much longer 

 than the spinous ; a short anal, a dentated preoperculum, an operculum termi- 

 nating in points, and seven branchial rays. If it were not for the absence of 

 the palatine teeth, these fishes would resemble the Perches. 



Naturalists divide it into various subgenera. Some of the species, such as 

 the King-fisher (an Umbrina), inhabit the American seas. 



The Scienoides, with a single dorsal, are subdivided according to the number 

 of their branchial rays. 



These divisions are H<xmulon, Pristoma, and Diagramma. 



The Scienoides with a single dorsal, and less than seven branchial rays, are 

 still more subdivided: in some of them the lateral line extends to the caudal; 

 in others it is interrupted. 



Those Scienoides which have less than seven branchial rays, and an in- 

 terrupted lateral line, form several genera of small oval fishes, prettily coloured, 

 which may be distinguished by the armature of their head. They are mani- 

 festly related to the genus Chaetodon, and resemble, externally, several of our 

 fishes with labyrinthian branchiae. 



The genera are Amphiprion, Premnas, Promacentrus, &c. 



