162 CONTRIBUTIONS TO AUSTRALIAN ICHTHYOLOGY, 



in front of the fish, the luminosity of the mandibulary organs 

 would, when the mouth was open, be patent to any animal 

 approaching from the side or behind, and would thus prove a 

 valuable adjunct to the symphysial disc of the upper jaw; while 

 the mere act of closing the mouth would shut off the light when- 

 ever its presence was liable to prove a source of danger. 



Again, the author of the ichthyological portion of Lydekker's 

 "Royal Natural History" writes of Monocentris jajionicus as 

 having the scales "articulated together so as to form a solid 

 armature." Whatever may be the case with regard to the 

 Japanese fish I do not know, not having a specimen for examina- 

 tion, but it is certain that no such articulated coat of mail exists 

 in the Australian species; on the contrary, the scales are normally 

 developed, though greatly thickened and embossed, and, far from 

 forming a " solid armature," are only partially imbricated, 

 especially on the tail, so that the naked skin is plainly visible 

 through the interstices, as is observable with many snakes. 



If the statement as to the articulation of the scales is 

 correct, and if the luminous organs, which are so conspicuous 

 in the Australian form, are wanting in the Japanese, there can 

 be no doubt that our fish must be relegated to a different genus; 

 but in the absence of special information on these points, I am 

 not prepared to go so far, and shall, therefore, for the present, 

 consider De Vis' Cleidopus as a subgenus of Monocentris, restrict- 

 ing the latter name to those species in which the vomer is toothless. 



In the '' Study of Fishes," Giinther announces t\\a.t Monocent7'is 

 is found at Mauritius, but as I have failed to find any earlier or 

 fuller record of such occurrence, I am unable to decide whether 

 the Mauritian fish belongs, as would seem more probable, to our 

 type or to that of the North Pacific. 



Monocentris. • 



Monocentris, Bloch and Schneider, Syst. Ichth. p. 100, 1801. 

 Lepisacanthus, Lacepede, Hist. Nat. Poiss. iii. p. 321, 1802. 

 Cleidojms, De Vis, Proc. Linn. Soc. N.S. Wales, vii. 1882, p. 367. 



* Royal Natural History, v. p. 354. The statement is not, so far as I 

 am aware, confirmed by other authors. 



