AMIOIDET. 



181 



the arches into the notochordal sheath. Fulcra 'present or absent. 

 Branchiostegal rays flattened ; a -median jugular plate. Teeth 

 pointed, conical. From the Lias onwards. 



This order, which is close to the Lepidostei, contains the 

 single living genus Amia. It approaches more closely to the 

 Teleostei than any other ganoid fish, but it differs from them 



•pmt 



Fia. ]09. — Meso'lon jnacropterus, restored, with cheek-plates removed, two-thirds 

 natural size. Upper Jurassic (after Smith Woodward), fr frontal, vteth mesethmoid, 

 md mandible, op operculum, orb orbit, p.op prooperculum, pa parietal, pmx 

 premaxilla, socc supraocclpital, sg squamosal, v vomer. (The caudal region is 

 destitute of scales in this fish.) 



in important features of the urinogenital organs and structure 

 of the heart, and alimentary canal. 



Fam. 1. Pachycormidae. Extinct. Etlimoid region more or less 

 produced in front of the movith ; vertebral column variable as in the 

 order. Fulcra present, branchiostegal rays numerous. Lias to Lower 

 Cretaceous. Packycormus Ag., Euthynotus Wagn., Hypsocormiis Wagn. 



Fam. 2. Amiidae. Vertebral column ossified with complete amphi- 

 coelovis vertebrae. The caudal region consisting of vertically divided 



