'61. NOVACULA. 169 



Novacula, Xyrichthys, Hemipteronotus, et Novaculichthys, Bleek. 



Proc. Zool. Soc. 1861, p. 414. 

 Novacula, Iniistius, Xirichthys, et Malacocenti-us, Gill in P)'oc. Acad. 



Nat. Sc. Philad. 1862, p. 143. 



Body compressed, oblong, covered with scales of moderate size ; 

 head compressed, more or less elevated and obtuse, with the upper 

 profile generally more or less parabolic ; head nearly entirely naked, 

 or with small scales on the cheek ; lateral line interrupted. No 

 posterior canine tooth, Formula of the fins : D- ^- ^'^'> the two 

 anterior dorsal spines sometimes remote or separate from the others. 



Seas between the tropics, extending northwards to the Mediter- 

 ranean and the Japanese and Californian Seas, southwards to the Cape 

 of Good Hope and Australia. 



The length and position of the two anterior dorsal spines, some 

 slight differences in the position of the ventral fins, the presence or 

 absence of scales on the cheeks, and, finally, the form of the upper 

 profile of the head, have been used as generic characters ; but as each 

 of these characters stands alone, and as the transitions between the 

 extreme forms are very numerous, I am inclined to leave these fishes 

 together in one genus. It is true that there is, apparently, a con- 

 siderable external difference between N. cultrata and N. macrole^i- 

 dota, hnt N. tceniurus and N. altiveUs are intermediate between both. 



The species may be divided as follows : — 



A. Cheek scaleless * ; no anterior division of the dorsal fin : Xirichthys 



et Malacocentrus, Gill. 



a. Upper edge of the head sharp : Novacula, Bleek., p. 169. 



b. Upper edge of the head rather obtuse ; Novaculichthysy pt., Bleek., 



p. 172. 



B. Cheek with two or three series of scales ; no anterior division of the 



dorsal fin : Novaculichthys, pt., Bleek., p. 174. 



C. Cheek scaly ; no anterior division of the dorsal fin, p. 174. 



D. Cheek scaleless ; the two anterior dorsal spines form a more or less 



separate division : Iniistitis, GUI. 



a. Upper edge of the head sharp : Xirichthys, Bleek., p. 175. 



b. Upper edge of the head rather obtuse : Novaculichthys, pt., Bleek., 



p. 176; 



E. Cheek scaly ; the two anterior dorsal spines form a more or less sepa- 



rate division : Hemipteronotm, Bleek. = Novacula, Gill, p. 177. 



A. Cheek scaleless ; no anterior division of the dorsal fin. 

 a. Upper edge of the head sharp. 



I. Novacula cultrata. 



Novacula, Plin. xxxii. c. 2 ; Rondel, v. c. 17. p. 146 ; Gesner, pp. 628, 

 629 & 721, and Paralip. p. 24; Willughb. p. 214. pi. 0. 2; iJay, p. 101. 



* This expression does not exclude those species which have a few rudimentary 

 scales behind or immediately below the orbit. 



