258 MR C. TATE REGAN ON THE 



the vertebral centra are thin cylinders of bone, parapophyses are developed on the 

 posterior praicaudals only, and the ribs and epipleurals are feeble. 



Si/no2ms of the Genera. 



I. Body scaly ; gill-membranes forming a fold across the isthmus ; opercles normal. 



A. Hypercoracoid enclosing its foramen. 



Lateral line scales with tubules or pits . . . 1. Trematomus. 



Lateral line scales merely notched. . . .2. Pleuragrainma. 



B. Foramen partly bordered by hypocoracoid. 



L Two or three lateral lines ; maxillary usually extending to below eye : 

 pectoral rounded or vertically truncated. 

 Teeth in bands ......... 3. Notothenia. 



Teeth uniserial ........ 4. Dissostichus. 



2. One lateral line ; maxillary not reaching eye in the adult fish ; pectoral 



very obliquely truncated, the upper rays longest . 5. Eleginops. 



IL Body naked ; gill-membranes broadly united to isthmus ; operculum hooked 



upwards posteriorly, its upper edge deeply concave ; foramen partly bordered 



by hypocoracoid. 



A mental barbel ; opercles not .spinate ....(>. Artedidraco. 



No barbel ; operculum and suboperculum each forming a strong spine. 



7. Harpagifer. 



L Trematomus, Bouleng., 1902. 

 "Southern Cross" Pisces, p. 177. 



Body scaly ; 2 lateral lines with tubular or pitted scales. Mouth moderate or 

 rather large ; jaws with bands of villiform teeth. Gill-membranes united, free or 

 forming a free fold across isthmus. Skeleton well ossified; vertebrae 52-56 (17-21 

 -h 32-35); most of the prsecaudals with parapopliyses to which the ribs and epipleurals 

 are attached ; hypercoracoid enclosing its foramen (fig. 3, 2). A spinous dorsal fin : 

 pectoral rounded or sub-vertically truncated. 



Coasts of the Antarctic Continent ; South Orkneys and South Georgia (fig. 5, p. 254). 



The difference between Notothenia, with the hypocoracoid bordering the foramen, 

 and Trematomus, with the foramen enclosed in the hypercoracoid, may not be very 

 important, and Pappenheim believed that he found both conditions in one species 

 [Deutsche Sudpolar-Exped., xiii., ZooL, v. p. 16(), figs.); but this seems to have been 

 an error, the specimen with perforate hypercoracoid being Trem,atomus hansom and not 

 Notothenia lepidorhinus. Pappenhkim {t.c, p. 170) states that T. bernacchii is a 

 Notothe7iia in the structure of its pectoral arch ; 1 have examined a large series of 

 specimens, and find that the hypercoracoid encloses its foramen in all. 



