136 Mr. C. T. Regan on the 



than the corresponding myotomes. Vertebra? 21 + 2G; ribs, 

 except the first 2 or 3, on strong parapophyses. 



Division 7. Trichodontiformes. 



This division includes a single family, differing from the 

 rcrciformes in the pectoral fin-skeleton. 



Fam. Trichodontidse. 



This family includes 2 genera. Trichudun and Arctoscopus, 

 related to the Perciformes. The external characters are 

 given by Jord. & Evcrm. (Bull. U.S. Nat. Mus. xlvii. p. 2295, 

 figs. 806, 807). The principal ostcological characters of 

 Trichodon trichodon are as follows : — Skull Oattish above, 

 without crests or ridges on upper surface ; suborbitals ossi- 

 fied, without subocular shelf; jaws normally formed, the 

 maxillary broadest distally, without supramaxillary ; meso- 

 pterygoid vestigial or absent; head skeleton otherwise 

 apparently Perciform. Post-temporal forked ; hypercora- 

 coid and hypocoracoid separated ; radials 4, rather large 

 and laminar, only the uppermost on the hypercoracoid. 

 Pelvic bones rather long and narrow. Vertebrae 49 

 (17 + 32); posterior praecaudals with parapophyses; ribs 

 on parapophyses when these are developed. 



Division 8. Ammodytiformes. 



Fam. Ammodytidae. 



Body elongate, naked or scaly. Vertical fins without 

 spines, the dorsal rays nearly equal in number to the 

 vertebrae below them, the caudal of 15 principal rays, 

 13 branched ; pectorals rather low ; pelvic fins, when 

 present, jugular, very small, of a spine and 3 soft rays. 

 Snout rather long and pointed ; eyes lateral ; mouth 

 protractile, terminal, with the lower jaw prominent ; prae- 

 maxillary slender ; maxillary not exposed, without supra- 

 maxillary, proximally with an anterior expansion or process, 

 which meets its fellow above the short preemaxillary 

 pedicels ; teeth in jaws minute or absent ; palate toothless. 

 Gill-membranes free from the isthmus ; 4 to 8 branchi- 

 ostegals ; 4 gills ; pseudobranchiee. Head-skeleton normally 

 Percoid as regards number and arrangement of bones ; 

 suboperculum very large, projecting considerably beyond 



