27. LEPIDOSTEID^. 89 



Br*icbiostegals present. Coronoid bone and praecoracoid arch present. 

 Arterial bulb with several pairs of valves. Optic nerves forming a chi- 

 asma. Intestine with a spiral valve. Air-bladder cellular, lung- like, cou- 

 iiected by a sort of glottis with the oesophagus. Tail hcterocercal. Skin 

 covered with scales, which are ganoid or cycloid. As here understood, 

 this group consists of the two orders Ginglymodi and HalecomorpJd, 

 the CroHmpterygia being considered as forming a distinct subclass. The 

 Chondrostei, Holostei, and Crossopterygia form the series or subclass 

 Ganoidei, represented by five widely divergent families among recent 

 fishes and by a great variety of extinct types. These forms, so far as 

 known, agree in a number of respects already indicated, and differ from 

 all the Teleostei, or ordinary fishes, in the presence of several i)airs of 

 valves in the arterial bulb, and in the presence of the optic chiasma. 

 The relations of the RalecomorpM with the Teleostean order of Isospon- 

 dyli are, however, undoubtedly very close. 



(Ganoidei Holostei part Giiuther, viii, 324-325, 328-331. oXog, complete; bareov, 

 bone.) 



ANALYSIS OF ORDERS OF HOLOSTEI. 



* Vertebra} oxjistlioccelian ; maxillary bone transversely divided into several pieces. 



Ginglymodi, I. 

 ** Vertebraj amjjbicceliau ; maxillary bone not transversely divided. 



Halecomorpiii, J. 



Oedee I.-GINGLYMODI. 



{The Gar Pilces.) 



Parietals in contact. Pterotic, basis cranii, and anterior vertebrae 

 simple. Symplectics present. Mandible with opercular, coronoid, an- 

 gular, articular, and dentary bones. Third superior pharyngeal small, 

 l^jng on fourth. Upi)er basihyal wanting. Maxillary transversely 

 divided. A cartilaginous praecoracoid arch. Vertebra} opisthocoelian. 

 Pectoral fins with mesopterygium and five other basal elements. Tail 

 heterocercal. This order includes the single family Lepidosteidce. 

 {ycyyXu/j.d<;, hinge; dcJwur, tooth. 



Family XXVIL— LEPIDOSTEID^. 



{The Gar Pikes.) 



Body elongate, subcylindrical, covered with hard, rhombic, ganoid 

 scales or plates, which are imbricated in oblique series running down- 

 ward and backward. Both jaws more or less elongate, spatulate or 

 beak-like, the upper jaw projecting beyond the lower. Premaxillary 



