The Ganoids 23 



Woodward places these fishes with the Semionotidcs and Ha- 

 lecomorphi in his suborder of Protospondyli. It seems preferable, 

 however, to consider them as forming a distinct order. 



Order Lepidostei. We may place, following Eastman's edition 

 of Zittel, the allies and predecessors of the garpike in a single 

 order, for which Huxley's name Lepidostei may well be used. 

 In this group the notochord is persistent, and the vertebrae are 

 in various degrees of ossification and of different forms. The 



FIG. 13. Mesturus verrucosus Wagner. Family Pycnodontidw. 

 (After Woodward.) 



opercles are usually complete, the branchiostegals present, and 

 there is often a gular plate. There is no infraclavicle and the 

 jaws have sharp teeth. The fins have fulcra, and the supports 

 of the fins agree in number with the rays. The tail is more or less 

 heterocercal. The scales are rhombic, arranged in oblique series, 

 which are often united above and below with peg-and-socket 

 articulations. This group contains among recent fishes only the 

 garpikes (Lepisosteus) . They are closely allied to the Palaonis- 

 cid&, but the skeleton is more highly ossified. On the other 

 hand they approach very closely to the ancestors of the bow- 

 fin, Amia. One genus, Acentrophorus, appears in the Permian; 

 the others are scattered through Mesozoic and Tertiary 

 rocks, the isolated group of gars still persisting. In the gars 

 the vertebrae are concavo-convex, with ball-and-socket joints. 

 In the others the vertebras are incomplete or else double-con- 

 cave, as in fishes generally. 



