FISHERY BULLETIN: VOL. 76, NO. 3 



Fraser-Brunner 

 Scott 1957:154 



Atopomychteriis nychthemerus: Giinther 

 1870:315 (South Australia, Tasmania). 



Diodon spinossisimus (not of Cuvier): Castelnau 

 1872:290 (Australia). 



IDiodon blochii? Castelnau 1872:210 (Australia). 



Atopomychteriis nichthemerus: Waite 1923:229 

 (South Australia, Tasmania). 



Dicotylichthys nychthemerus : 

 1943:17 (Australia). 



Atopomycterus uicthemerus: 

 (Tasmania). 



Diodon nycthemerus: Le Danois 1959:227 (Aus- 

 tralia). 



Atopomycterus nicthemerus: Scott 1962:299 

 (West Australia, South Australia, Tasmania). 



Diagnosis. — Round-bodied Diodon, head width 

 0.34-0.43, peduncle length 0.12-0.16. Caudal 

 peduncle without spines. Body spines long and 

 narrow, but relatively few in number, S-D spines 

 9-12, S- A spines 10-11. Pectoral axil spines shorter 

 than longest frontal spines. No short, fixed tribase 

 spine immediately above gill opening. Fin ray 

 counts low, D 12-13, A 12-14, P 19-21. Nasal tenta- 

 cle with a pair of lateral openings which are sepa- 

 rated by a thin membrane; this is often absent 

 (more often in larger individuals) resulting in the 

 nostrils appearing "confluent, each nasal organ 

 appearing as a bifid tentacle" (Fraser-Bruner 



1943:16). Fins without dark spots. Individuals 100 

 mm and greater with four dark bars on the sides 

 and lacking dark spots on the body. 



Description.— { 10 specimens) D 12-13, the first un- 

 segmented; A 12-14, the first unsegmented; P 

 19-21; vertebrae 9 + 12-21 (Gunther 1870). 

 Head width 0.34-0.43 ix = 0.39; SD = 0.03), body 

 width 0.39 - 0.52 (x = 0.45; SD = 0.05), peduncle 

 length 0.12-0.16 (x = 0.14; SD = 0.01), eye 0.09- 

 0.17 ix = 0.12; SD = 0.02) greatest in smaller 

 specimens. Dorsal, anal, and caudal fins all 

 rounded, middle rays longest. Nasal tentacles 

 with a pair of lateral openings which are separated 

 by a thin membrane which is often broken or re- 

 sorbed, especially in larger individuals, resulting 

 in the nasal organ appearing as a bifid tentacle. 

 S-D spines 9-12, S-A spines 10-11, about 9 spine 

 rows over dorsum between pectoral fin bases, 

 about 15 spine rows over ventrum between pec- 

 toral fin bases. Five frontal spines. Longest frontal 

 spines 0.15-0.23 ix = 0.19; SD = 0.03), greatest in 

 smaller specimens, pectoral axil spines 0.11-0.20 

 ix - 0.15; SD - 0.03). Frontal spines longest on 

 body; 1.12-1.35 (x = 1.25; SD = 0.08) times pec- 

 toral axil spines, although many dorsal spines 

 nearly as long. Ventral spines shorter than dorsal 

 spines (ca. 1.4 in dorsal spines). Lateral spines 



FIGURE 13.— Diodon nicthemerus, 110 mm SL, Victoria, Australia (AMS 1.16990-004). 



550 



