428 PROCEEDINGS OF THE NATIONAL MVSEVM. vol.50. 



KEY TO THE SPECIES OF NOTOTHENIA OF THE WATERS OF SOUTH AMERICA, INCLUDING 



THE FALKLANDS. 



a^. Snout very short, measured to the edge of the eye about 5 in head; maxillary 

 3J to 4 in head; interorbital width 4f to 5 in head; dorsal VI, 32; anal 30; 

 scales 70 to 73; pectoral about 1-^ in head; caudal peduncle depth 3 to 3f in 

 same; gill rakers 9+12; scales between occiput and dorsal insertion 15. 



N. gilberti, 1. 

 a^. Snout longer, contained 3 or 4 times in head. 

 b^. Head scaleless above or nearlj^ so. 

 c^ Width of interorbital sj^ace more than three-tenths that of the head; anal 

 base 2J to 2^ in body; anal 24 or 25; scales 55 to 75; scales transverse 26; 

 length of ventral If to 1 J in head. 

 e?'. Scales smooth to touch; 55 to 65 in lateral series; pores in upper lateral 

 line 37 to 46; scales covering space in front of and between ventrals. 



N. tnacrocephala, 2. 



d^. Scales plainly ctenoid to touch; 65 to 75 in lateral series; pores in upper 



lateral line 50 to 60; scales lacking in front of and over half of distance 



between ventrals N. latifrons, 3. 



c^. Width of interorbital space less than one-fifth length of head; anal base 2 in 

 body; anal rays more than 26; scales less than 55. 

 c^ W^idth of interorbital space one-tMrteenth to one-fifteenth that of head; 

 length of head one-fourth to three-tenths of body length; depth of 

 body 6f to b^^ in its length; maxillary about 3 or 3 J in head; dorsal 

 VI, 33; depth of caudal peduncle slightly less than diameter of eye; 

 velum narrow; two series of scales between dorsal fin and lateral 



line N. elegans, 4. 



e^. Width of interorbital space one-sixth length of head; head 3J to 2| in 



body; depth of body 4f to 5 in its length; maxillary about 2h to 3 in 



head; dorsal V or VI, 28 to 33; depth of caudal peduncle greater than 



diameter of eye. 



p. Dorsal V, 31 to 33; scales in lateral series 49 to 54; opercle scaled above 



only; no embedded scales on interorbital space; base of pectoral 



with a distinct bar completely across it in adults iV. cornucola, 5. 



/■-. Dorsal VI (rarely V), 27 to 30; scales 45 to 49; opercle scaled entirely; 

 a single embedded scale always present on anterior part of interorbital 

 space (surface of head sometimes entirely scaled); bar on pectoral 



base not extending completely across it N. sima, 6. 



6 2. Head distinctly scaled above. 



gK Anal rays 28 to 30; dorsal V to VII, 26 to 31; scales 46 to 50; depth of 

 caudal peduncle 3^ in head; ventrals extending to or well beyond 

 anus. 

 h^. Head cylindrical, cottoidlike, somewhat depressed; width of inter- 

 orbital space 6 in head; eye slightly dorsal in position and out- 

 look; dorsal V or VI, 28 to 30; gill rakers X+9 to 12; scales on 

 head small, much smaller than those on body, frequently nearly 

 entirely absent; anal with oblique stripes, ventral clear. (See 



above.) N. sima, 6. 



h^. Head compressed laterally; body very deep, its width about If 

 in its depth; width of interorbital space 4J to 5 in head; eye 

 facing laterally; dorsal VI or VII, 26 to 29; gill rakers 8+13 to 

 16; scales on head large, nearly as large as those on body, never 



absent N- squamiceps, 7. 



g^. Anal rays 30 to 34; dorsal V to VIII, 32 to 36; scales in lateral series 

 above lateral line 55; depth of caudal peduncle contained 3^ in 

 head or more (except in N. hrevicauda); ventrals ending at or 

 before anus in adults. 



