MESODON. 



49 



not sufficiently expanded to meet round the notochord. Fin-rays robust, articulated, 

 and divided distally. Pelvic fins present; dorsal and anal fins deep throughout 

 their extent, the former occupying the hinder halt' of the back, and the latter 

 somewhat shorter ; caudal fin fan-shaped, with a truncated or convex hinder 

 margin, and arising immediately between the posterior extremities of the dorsal 

 and anal fins. Scales usually smooth, covering only the anterior half of the trunk, 

 and complete only in the lower part of the flank. 



Type Species. — Mesodon macropterus (A. Wagner, lor. rif., 1851, pp. 49, 56, 



Fia. 20. — Mesodon macropterus (Agassiz) ; restoration, about two-thirds nat. size. — Lower Kimmeridgian 

 (Lithographic Stone) ; Bavaria, fr., frontal ; m.eth., mesethmoid ; md., mandible, showing narrow 

 dentary in front; op., operculum ; orb., orbit; p.'ip., preoperculum ; pa., parietal ; pas. , parasphenoid ; 

 pmx., premaxilla ; s. occ , supraoccipital ; sq., squamosal ; u., vomer. 



pi. iv, fig. 2) from the Lower Kimmeridgian (Lithographic Stone) of Kelheim, 

 Bavaria. The species had previously been named Gyrodtis macropterus by 

 L. Agassiz, Poiss. Foss., Feuill. (1834), p. 18, and vol, ii, pt. ii (1844), p. 301. 



Remarks. — In a restoration of the type species of Mesodon published in my 

 'Outlines of Vertebrate Palaeontology ' (1898), the arrangement of the scales is 

 wrongly based on the Liassic species now named Eomesodon liassicus (see below, 

 p. 55). A new restoration is accordingly given in the accompanying Text-fig. 20. 



In a restoration of Mesodon bcrnissartensis, from the Wealden of Belgium, 

 published by R. II. Traquair in his " Poissons Wealdiens de Bernissart " (Ann. 



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