1902.1 



PLECTOGNATnOUS FISHES. 



293 



Xenopterus and Chonerhinus, on the contraiy, it has become 

 excessively developed. 



Dr. Gill (Proc. U.S. N. M. xiv. pp. 705-720, pi. xxxiv. (1890)) 

 has arranged the fishes which I here include in the family Tetro- 

 dontidfe in three families : Tetrodontidse, OhonerhinicWj and 

 Canthigasteridfe, which are chiefly distinguished by supposed 

 cranial difTerences. In the Oanthigasteridte and Chonerhinidse 

 the post-frontals are said to meet in the middle line, thus sepa- 

 rating the frontals from the supraoccipital. An examination of 

 the skeletons has convinced me that in these fishes the post- 

 frontals are confined to the sides, and that the frontals are in 

 contact with the supraoccipital. The erroneous statements and 

 figures of Hollard have met with too ready an acceptance, that 

 author having mistaken ridges on and fissures in the frontal 

 bones for sutures between them and the post-frontals. The 

 Oanthigasteridaa are also defined as having a long prominent 



Text-fio". 58 



CO. 



A. Skull of Tetrodoii sceleratus, seen from above (on the right the postero- 



lateral process of the frontal has been removed). 



B. Skull of Tropidiclithys papua, seen from above. 



C. „ „ „ side view. 



J5W., premaxillary; w., maxillary ; jpn?., palatine ; etJi., ethmoid ; prf., praefrontal ; 

 /., frontal ; ptf., postfrontal ; gq.. squamosal : par., parietal ; ev.. esoccipital .: 

 so.j .supraoccipital. 



