27. LEPIDOSTEIDJ2. 89 



Brafachiostegals present. Coronoicl bone and proecoracoid arch present. 

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

 asma. I ntestine with a spiral valve. Air-bladder cellular, lung-like, con- 

 nected by a sort of glottis with the oesophagus. Tail heterocercal. Skin 

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

 this group consists of the two orders Ginglymodi and Halecomorphi, 

 the Crossopterygia being considered as forming a distinct subclass. The 

 Chondrostei, Holostei, and Grossopterygia 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 Tcleostei, or ordinary fishes, in the presence of several pairs of 

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

 The relations of the Halecomorphi with the Teleosteau order of Isospon- 

 dyli are, however, undoubtedly very close. 



(danoidei Holostei part Gii.nth.er, viii, 324-325, 328-331. 6/lof, complete; OOTEOV, 

 bone.) 



ANALYSIS OF ORDERS OF HOLOSTEI. 



* Vertebrae opisthoccelian ; maxillary bone transversely divided into several pieces. 



GINGLYMODI, I. 

 ** Vertebrae amphicoelian ; maxillary bone not transversely divided. 



HALECOMORPHI, J. 



OKDEE I -GINGLYMODI. 



(The Gar Pikes.} 



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

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

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

 lying on fourth. Upper basihyal wanting. Maxillary transversely 

 divided. A cartilaginous praecoracoid arch. Vertebrae opisthocoelian. 

 Pectoral fins with mesopterygium and five other basal elements. Tail 

 heterocercal. This order includes the single family Lepidosteidcv. 

 hinge; o'oou-, tooth. 



FAMILY XXVII. LEPIDOSTEID^E. 



(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. Preinaxillary 



