8 DISCOVERY REPORTS 



separated by an interspace, and each formed of a spine and 5 branched rays. There 

 is a single nostril on each side. In osteological characters the more generahzed forms 

 are very similar to the Perciformes, but the structure and position of the radials of the 

 pectoral fins are highly characteristic. The radials are 3 in number, rather large flat 

 plates ; all or 2 are inserted on the hypocoracoid, and the lowest is the narrowest and 

 has its lower edge in contact with the metapterygoid process. [After Regan.] 



Five families, of which one (Bovichthyidae) does not occur in the Antarctic Zone. 



Synopsis of the Antarctic Families 



I. Palatines and pterygoids normally developed; ribs present. 



A. Spinous dorsal fin present; mouth protractile. 



1. Operculum normal; body scaly; gill-membranes forming a fold across the isthmus 



I . Nototheniidae. 



2. Operculum hooked upwards posteriorly, its upper edge deeply concave; body 

 naked; gill-membranes broadly united to isthmus 2. Harpaaiferidae. 



B. Spinous dorsal fin absent; mouth usually non-protractile ... ... 3. Bathydraconidae. 



II. Palatine in great part ligamentous; no mesopterygoid ; mouth not protractile; snout pro- 

 duced and depressed; ribs not ossified ... ... ... ... ... 4. Chaenichthyidae . 



Family NOTOTHENIIDAE 



Body scaly. Snout not or only a little produced. Mouth protractile; palatines and 

 pterygoids normally developed ; palate toothless. Gill-membranes forming a fold across 

 the isthmus ; operculum normal. Spinous dorsal fin present. All three radials situated 

 on the hypocoracoid. Ribs present. 



Five genera, of which one (Eleginops) does not occur in the Antarctic Zone. 



Key to the Antarctic Genera 

 I. Foramen partly bordered by hypocoracoid (fig. 3 b) i. Notothema. 



II. Hypercoracoid enclosing its foramen (fig. 3 a). 



A. Scales not very thin, those of upper lateral line with tubules, those of lower lateral line 

 with tubules or pits; two lateral lines; skeleton well ossified; most of the praecaudal 

 vertebrae with parapophyses 



1. Teeth in bands, villiform; snout not much longer than eye ... 2. Trematomus. 



2. Teeth in upper jaw biserial, those of outer row enlarged, spaced, canine-like; a 

 group of stronger teeth on each praemaxillary; teeth of lower jaw uniserial, spaced, 

 canine-like; snout much longer than eye 3. Dissostichus. 



B. Scales very thin, cycloid, those of the 3 lateral lines each with a notched hinder margin 

 and with a vertical row of 3 shallow pits; skeleton feebly ossified; only the posterior 

 praecaudal vertebrae with parapophyses 4. Pleuragramma. 



Genus NOTOTHENIA 



Notothenia, Richardson, 1844, Zool. 'Erebus' and 'Terror' (Fish.), p. 5; Gunther, i860, Cat. 

 Fish., n, p. 260; Regan, 1913, Trans. R. Soc. Edinburgh, XLix, p. 264. Type Notothenia 

 coriiceps, Richardson. 



