68 " THETIS " SCIENTIFIC RESULTS. 



In the paper above quoted, Ogilby has reinstated De Vis' species, 

 but as some of the contrasted characters are ill-founded I will first 

 deal with these. I have before me two small examples of M. 

 ja2Jonicus, obtained from Japanese seas, so that my comparisons 

 are actual, and herein I have the advantage, as Ogilby had not 

 seen Japanese material. 



The characters relied upon as specific were the nature of the teeth, 

 the presence of luminous organs in Australian specimens, and the 

 condition of the armament. 



Teeth. — With the exception of a rather dijBferent contour, 

 consequent on the varied shape of the jaws, to be referred to later, 

 the teeth of the two forms are quite similar, with the proviso that 

 in M. glo7'ia-maris there is a small rounded patch on the vomer. 

 This is absent in the Japanese form. 



Luminous organs. — These have been fully described in our 

 species, and I need not further refer to them, excepting to remark 

 that the mandibulary discs are most conspicuous objects. I can 

 find no trace of such organs in M. jajjonicus ; this is therefore an 

 important specific difference. 



Scales. — The character of the scales has not been insisted on, 

 but the writer quoted draws attention to the fact that the author 

 of the ichthyological portion of Lydekker's " Royal Natural 

 History " writes of Monocent7'is japonicus as having the scales 

 articulated together so as to form a solid armature, and adds : — 

 " The statement is not, so far as I am aware, confirmed by other 

 authors." 



A comparison shows that such differences as occur in the scales 

 are to be found in the sculpture, and not in the method of implanta- 

 tion or connection. In the small Japanese specimens at my 

 disposal the scales are more imbricate than in the lai"ger Australian 

 examples, but the numerous figures of M. japonicus certainly 

 indicate the black skin which separates the scales, so that no 

 great imbrication occurs. It is to be mentioned, however, that 

 the scales of the caudal pedicel are imbricate, while towards the 

 lower surface the scales in both species are not only imbricate but 

 are firmly locked together. Actual fusion scarcely occurs, for in 

 the smooth groove into which the ventral spine is received the 

 sutures between the scales can still be traced. 



Some further points of difference may now be considered. I 

 have no record of the size to which Monocentris jajjonicus attains, 

 but from the various accounts accessible, it seems to be a much 

 smaller species than ours, which reaches 230 mm. (9 inches) in 

 total length. 



If my Japanese examples are immature, the less ornate character 

 of the scales may be thus explained. In the Australian species 



