ORDER V. 



PLECTO.GNATHI. 



The premaxillar and maxillar bones are united into one continuous immovable bony piece. 

 The internal skeleton is but partly ossiffied. The opercular apparatus is hidden under a 

 thickened skin. Branchial apertures small. The surface of the skin is either protected with 

 enamelled scales, (ganoid,) else with asperities or spinous productions, characters by which 

 these fishes are always easily distinguished from those of the other orders. The swimming 

 or air bladder has no air duct in communication with the throat. 



Six.Plectognathes, Cuv. Tabl. elem. Hist. nat. Anim. 1798 ; Regn. Anim. II, 1817, 144 ; 2d ed. II, 1S23 ; &, ed. illustr. 

 Poiss. 333. 



Plectognathi, BONAP. Sngg. Distr. raetod. Anim. Verterbr. 1831, 120. RICHARDS. Faun. Bor. Arr.cr. Ill, 1836, 277. 

 DEKAY, New Y. Faun. IV, 1842, 323. MULL, in Wiegm. Archiv fur Naturg. 1845, 1, 134, & 137. STOKER, 

 Synops. 1846, 239. 



The family of Ostracionidae, the third of this Order, has furnished as yet no representatives 

 to the ichthyic fauna of our western coast, where, no doubt, some of them exist. Not being 

 marketable fishes, they are no object of attraction except to naturalists, who, so far, have had 

 but few opportunities to prosecute their explorations in that region of the country. 



A &quot;sun-fish,&quot; &quot;head-fish,&quot; or &quot;moon-fish,&quot; (Orlhagoriscus) as sometimes called, has been 

 observed off the harbor of San Diego, as I am informed by my friend Lieut. Trowbridge. 

 The &quot; moon-fish&quot; may wtll be considered as the type of a fourth family (Orthagoriacidae) 

 amongst the Plectognathians. 



Family EALISTIDAE,, Bonap. 



The body is compressed, rather short and deep, covered with either large or small scales, or 

 else with prickles, or granules. The snout is sub-conical and prolonged, terminated by a small 

 mouth provided with a few isolated teeth. There are two dorsal fins, the anterior one often 

 reduced to a single spine. The pelvic bone is prominent ; the ventral fins being, however, but 

 imperfectly developed. 



SYN. Balistidae, BONAP. Sngg. Distr. metod. Anim. Vertebr. 1831, 120. DEKAY, New Y. Faun. IV, 1842, 333. STOKER, 

 Synops. 184G, 243. 



Balistini, BONAP. Catal. metod. Pise. Europ. 1846, 88. MULL, in Wiegm Archiv fur Naturg. 1845, I, 134 & 137. 

 Balistides, DUM. Ichthyol. analyt. 185G, 177. 



A species of this family was received during the early part of the present year from San 

 Diego, California, where it was collected by A. Cassidy. The specimens having been mislaid 

 in the moving of the Smithsonian collections from one end of the building to another a few 

 mouths since, we are unabls at present to refer it to its proper genus, and give any further 

 description of the species, beyond stating that the specimens were of a jet black tint, with light 

 (either white or yellow) margined fius. 



