NO. 9 NEW DEEP-WATER FISHES MYERS 



KEY TO GENERA OF TRIACANTHIDAE 



la. Front pair of teeth in each jaw wide compressed incisors, forming a beak; 

 caudal peduncle long ; mouth terminal ; spinous dorsal 5 ; pseudobranchiae 

 present, little developed, confined to upper part of opercular wall. (Sub- 

 family Triacanthinae. ) Triacanthus. 



lb. Front pair of teeth in each jaw not enlarged incisors, rather small, conical or 

 compressed, and never forming a beak ; caudal peduncle comparatively- 

 short. 

 2a. Snout greatly prolonged, tubular, the tiny mouth at the tip, directed 

 upward; dorsal spines 2 or 3. (Subfamily Halimochirurginae.) 

 3a. Teeth present in both jaws, conical; lips not greatly flattened; dorsal 



spines 2 or 3 Halinwchirurgus. 



3b. Teeth present only in lower jaw, incisors with truncate tips ; lips wide, 

 forming a flattened, suckerlike disk ; dorsal spines 3. 



Macrorhamphosodes. 

 2b. Snout not greatly prolonged; dorsal spines 4 or more. (Subfamily Tri- 

 acanthodinae. ) 

 4a. Teeth truncated incisors ; dorsal spines 4, the last imbedded deeply ; 

 lips very thick ; mouth very strongly directed upward, almost super- 

 ior ; fin spines with strong retrorse hooks ; pseudobranchiae con- 

 fined to upper half of opercular wall Tydemania. 



4b. Teeth conical; dorsal spines 5 or more (except in Bathyphylax), the 



last deeply imbedded ; lips moderate or thin ; mouth terminal or 



directed upward, never superior. 



5a. Branchial openings comparatively wide, extending below lower edge 



of pectoral base; pseudobranchiae very well developed, extending 



far below middle of opercular wall ; dorsal origin anterior ; teeth 



strong and few, a pair of conical teeth behind main series in each 



jaw indifferently present or absent; dorsal spines 5 or 6. 



Triacanthodes. 

 sb. Branchial oi)enings restricted, not extending downward as far as 

 lower part of pectoral base ; pseudobranchiae confined to upper 

 half of opercular wall (not examined in Hollardia or Bathy- 

 phylax) ; conical teeth behind main series usually absent. 

 6a. Dorsal set posteriorly, distance between snout tip and base of first 

 dorsal spine greater than half standard length ; dorsum rising 

 to a point at first dorsal spine, the base of dorsal fins obliquely 

 descending ; teeth large, strong and few ; dorsal spines 6. 



Hollardia. 

 6b. Dorsal set anteriorly, distance between snout tip and base of first 

 dorsal spine considerably less than half standard length ; dorsum 

 truncate, the base of the dorsal fins in adults approximately 

 horizontal. 

 7a. Teeth strong and few, about 10 in each jaw; dorsal spines 6, 

 the last almost invisible ; conical teeth behind main row occa- 

 sionally present ; eye moderate Paratriacanthodes. 



7b. Teeth weak and many, 20 or more in each jaw, strictly in a 

 single series ; eye large. 



