1902.] 



PLECTOGNATHOUS PISHES. 



295 



A. 28-32), whilst the frontals have large postero-lateral expan- 

 sions, completely roofing-in the post- frontals, which are invisible 

 from above. 



[Since the reading of this paper I have been in communication 

 with Dr. Pellegrin of the Paris Museum, who has examined the 

 skeleton of Xenopterus hellangeri described by Hollard, and also 

 the spirit-specimens referred to that species. These latter he is 

 unable to distinguish from X. naritus Richardson ; but the skull 

 figured by Hollard differs considerably from that of X naritus, 

 and, unless these differences should prove to be sexual, must be 

 regarded as belonging to a distinct species, although the number 

 of vertebrae (29) and of fin-rays (D. 34, A. 29) are the same in 

 each case. 



In X. hellangeri the frontals are scarcely thickened, they show 

 lines resembling sutures, corresponding to similar lines in Chone- 

 rhinus modestus Bleeker, and due to the texture of the bone, and 



Text-fig. 59. 



\---'^i par. 



Skulls of (A) Chonerhmus modestus, (B) Xennpterus hellangeri, and (C) Xenopterus 

 narihis, seen from above ; in the latter the left postero-lateral extension ot the 

 frontal has been cut away. Lettering as in text-tig. 58. 



their postero-lateral expansions do not extend over the parietals 

 and squamosals. X. naritus diff'ers in having very thick frontals, 

 without any trace of lines of ossification and even the median 

 suture obscure, and with strong postero-lateral expansions roofing- 

 in parietals and squamosals. 



Through the kindness of Dr. Pellegrin, to whom I take this 

 opportunity of expressing my gratitude for the trouble he has 

 taken, I am enabled to reproduce a drawing of the skull ^ of 

 X. hellangeri already figured by Hollard, for comparison with 

 those of X naritus and Chonerhinus modestus. Hollard's skeleton 

 must be regarded as the type of X hellangeri ; it is 280 mm. in 

 total lenffth.— i)ec. 20, 1902.] 



