622 



SCANDIXAVIAX FISHES. 



composite dental growths, one or two in eacli jaw, 

 which project like a I>eak beyond tlie lips — hence the 

 name of les Gymnodontcfi, from yvuro^^ naked and od'ovg^ 

 toofJi. Of these families the latter is distinctly more 

 perfectly Plectogiiate in its chai-acters. At the present 



time we generally follow Bonaparte" and di\ide these 

 fishes into four families, two within each of the Cu- 

 vierian faujilies''. Only two species, each representing 

 a distinct family, have lieen found within the limits 

 of the Scandinavian fauna. 



fam r t h a g OB I s c 1 1) j^:. 



Gymnodonts with stunted trunk, hodji compressed laterally (round or elliptical) and not distensirc, and continuous 

 verticcd fins. Dental disks of the jaws undivided. Pseudohranchifc larye. Air-hlaildcr'', pelvic bones. 



and ventral fins wantiny. 



With an appearance as though they were of the 

 normal piscine form but with truncate tail, these Lagy- 

 bukar ( Tmi-bellies) — as Retzius called them together 



l.iS. Skeletou of Orthaijorisciis moUi, 

 After Welleniserc 



.., of the naturnl size. 



with the rest of the Gymnodonts — deservedly excite 

 attention even by their external characters. In form 

 and ai)])earance tiiey remind us somewhat of the Opah; 

 but merely a casual examination is enougli to show 



that they are of an entirely different type. Tlie\- reallv 

 rank among the most singular piscine forms. The 

 stunted appearance of the body depends, it is true, on 

 the comparatively small number of the vertebra; (IG 

 or 17); but this number may be still smaller in the 

 Coffer-fishes. The short form of the body is really 

 caused by its depth posteriorly, this lieing due to a 

 prominent development of the upper and lower arches 

 of the vertebriB, with their spinous processes, in the 

 caudal part of the body, and t)f the interneural spines 

 of the dorsal fin and the interhu'mal spines of the anal 

 fin (fig. 153). This de\iation from the other Plecto- 

 gnates is connected with an extremely unusual course 

 of development. 



In the middle of the last century Kolreuter'' gave 

 an excellent descri]>tion and a figure of no small merit, 

 considering the period of its execution, of a fish 16 

 mm. long and 19^3 mm. deep, "which at a casual 

 glance might easily be taken for a head cut off from 

 the trunk, and nothing more." Closer examination 

 soon showed, ho^\'e\"er, that this specimen was a young 

 form of Orthayoriscus (Tetrodon) mala, as Linnaeus' 

 interpreted this find. But the most .singular circum- 

 stance was that it had no caudal fin whatever. In 

 another specimen, 40'/, nun. long and 4il\,., mm. dee}), 

 on the other hand, Kolreuter found a distinct, cre- 

 luilated caudal lobe along the hind margin of the fish, 

 uniting the dorsal fin to the anal. Since that time 

 these small fisiies have been met with on numerous 



" Catalogo metodico dei pesci europei, p. 87. 



'' Bleeker (Atlas Ichtliyologiqiic, tome V) divided the Plectognates into three orders and these iigaiii iiiln f:uiiilies conespoiiding to 

 GUnther's suhfaniilies: Ostraciontina ; Triacanthinn, Dalistina; 7'riodontina, Telrodontina, Molina. 



' Costa {Fn. <J. Rcijii. i/i NapoU, tav. 6.^ e 04) describes aud Bgures a rudimentary air-bUidder in Ortliagorisciis viola. 



<* Nov. Comment. Ae.id. Sc. Petrop., vol. X (1706), p. .337, tab. \'III, Hgs. 2 and 3. Mola aculeata, limho abdomini." prudnrto. 

 aftenuato, carnoso. 



'■ Si/st. iiat.. ed. XII, tonj. 1, part. 2, Add. (in fine). 



