438 risHES. 



were inhabitants of considerable depths of the ocean. Both 

 the jaws of Palceorliynchios are prolonged into a beak, whilst 

 in HcmirTiynchus the upper exceeds. the lower in length. 



Eighth Division — Acanthoptekygii Cotto-scombeiformes. 



Spines developed in one of the fins at least. Dorsal fins 

 either continuous or close together ; the spinous dorsal, if pre- 

 sent, always short ; sometimes modified into tentacles, or into 

 a suctorial dish ; soft dorsal always long, if the spinous is 

 absent; anal similarly developed as the soft dorsal, and hoth 

 generally much longer than the spinous, sometimes tenninating 

 in finlets. Ventrals, thoracic or jugular, if present, never 

 modified into an adhesive apparatus. No prominent anal 

 papilla. 



Marine fishes, with few exceptions. 



First Family — AceonueidjE. 



Body compressed, ohlong or elevated, covered ivith minute 

 scales. Tail generally armed with one or more hony plates or 

 spines, which are developed with age, hut absent in very young 

 individuals. Eye lateral, of moderate size. Mouth small; a 

 single series of more or less compressed, sometimes denticulated, 

 sometimes pointed incisors in each jaw ; palate toothless. One 

 dorsal fin, the spinous portion being less developed than the soft ; 

 anal with two or three spines; ventral fins tJwracic. Air- 

 bladder forked posteriorly. Intestines with more or less 

 numerous circumvolutions. Nine abdominal, and thirteen 

 caudal vertebrce. 



Inhabitants of the tropical seas, and most abundant on 

 coral-reefs. They feed either on vegetable substances or on 

 the superficial animal matter of corals. 



Extinct species of Acanthurus and Naseus have been dis- 

 covered in the Monte Bolca formation. 



