ORDER TELEOSTEI. 



IOI5 



the upper jaw are generally welded together ; there is a soft dorsal 

 fin ; but the pelvic fins are either in the form of spines or absent. 

 There is no duct to the swim-bladder. 



Family Balistid^e. — The File-fishes and Coffer-fishes, which are 

 frequently known as Sclerodermic have the jaws somewhat produced, 

 and armed with a small number of teeth ; the skin being covered 

 either with rough scales or scutes, and traces of pelvic and spinous 

 dorsal fins always remaining. Balistes (File-fish) is characterised 

 by its chisel-like teeth, admirably suited for browsing on the corals 

 on which these fishes subsist. Protobalistum, of the Middle Eocene 

 of Monte Bolca, is supposed to be an ancestral type of Balistes ; 

 while P?-otaca?ithodes, of the same deposits, is an allied, but distinct 

 form. The Lower Eocene of Glarus has yielded the extinct Acan- 

 thoderma and Acanthopleurus^ which are likewise regarded as allied 

 types ; while Glyptocephalus, of the London Clay, differs from 

 Balistes by the regular rows of tubercles with which the body is 

 covered. Ostracion (Coffer-fish), in which the body is invested by 

 a carapace of hexagonal scutes articulating by their edges, is now 

 abundant in subtropical and tropical seas, and appears for the first 

 time in the Middle Eocene of Monte Bolca. 



Family Diodontid^. — In the Globe- and Sun-fishes (the Gymnod- 

 ontes of many writers) the body is more or less shortened ; the 

 bones of the jaws are united into a trenchant beak, with or without 

 a median suture ; and there are no spinous dorsal, or pelvic fins. 

 The dentition is in the form of . laminated dental plates. Among 

 the Globe-fishes, in Tetrodon, of which no fossil forms have been de- 

 scribed, the dental plates are trenchant, and confined to the margins 

 of the jaws. In JDiodon, however, in addition 

 to these alveolar plates, there is a median crush- 

 ing-plate (fig. 949), traversed by a suture, de- 

 veloped on the palate of each jaw. The ob- 

 liquity of the component laminae of these plates 

 causing an admirable triturating surface. Fossil 

 palatal plates of this genus are found in the 

 Miocene of Malta and Sicily, in the Middle 

 Eocene of Monte Bolca, and also in the 

 Eocene of Algeria and the Arakan coast. The 

 extinct Enneodon is an apparently allied genus 

 from the Italian Tertiary. Finally, the huge pelagic Sun-fishes of 

 the genus Orthagoriscus, in which the body is compressed and very 

 short, the vertical fins are confluent, and the tail truncate, occur in 

 a fossil state in the Lower Miocene or Upper Eocene of Belgium. 

 The alleged occurrence of this genus in the English Chalk is, how- 

 ever, based on a misinterpretation. 



At the conclusion of this order we may mention the genus 

 vol. 11. 1 



Fig. 949. — Posterior 

 dental plate of Diodott 

 Scillce ; from the Miocene 

 of Malta. 



