ILO EEPORT OF COMMISSIONER OF FISH AND FISHERIES. [4] 



Mie orbits, wliile tlieir anterior lateral augles rest upon the antorbital 

 processes. In view of this arrangement this pair of bones are charac- 

 terized as the frontalia'^ [frontal plates]. 



Behind these two bones, follow two others of an approximately quad- 

 rilateral outline, which like the preceding pair are connected together 

 in the middle line by a dentated suture. These are undoubtedly the 

 ossaparietalia [j)arietal plates], which in Amia, as in several other bony 

 fishes, are suturally united mesiad^. (Plate I, Fig. 1.) 



On either side of the parietalia and of the posterior part of the fronta- 

 lia is found a longitudinally placed bone (Plate I, Fig. 1, ISq.), which 

 corresponds in all respects with the os squamosum of the Teleostei.^ 



Articulating with its hinder border with the squamosal on either side, 

 and being situated at about the middle of the latter half of the frontal, 

 we observe another osseous plate, with its long diameter placed longi- 

 tudinally. It is the osseous plate that overlies the continuation of the 

 post-orbital, and is the i:)ost-frontal (Plate I, Fig. 1, and Plate II, Figs. 5 

 and 6, Psf.). A similar, only smaller, bone-plate, extensively sculptured, 

 articulates with the anterior lateral angle of the frontal, and is the 

 superimijosed plate that represents the prefrontal (Plate I, Figs. 1, 2, 

 and 3, Prf.). While the bony plates just described are firmly articulated 

 with one another, and are also in intimate relation with the true cranium 

 beneath, or are even blended with it, the two rather small osseous plates^ 

 (Plate I, Fig. 1, Ux.) situated behind the x)arietals and squamosals, and 

 meeting each other in the middle line,^ are connected only with the 

 bones in front of them by means of dense ligamentous bands. l^Tor 



^As regards the deteriniuatious of these Tboues, I have adhered strictly to the 

 names used for them by Gegenhaur. It is of course iiuiversally kuown that these 

 names, now long in use, do not express any homology whatever with the correspond- 

 ingly named hones of the higher vertebrated animals. I am of the oinuion that a 

 complete homology exists for only a very few of the bones of hshes when comjjared 

 with those of the higher vertebrata. There is not positive proof for a single one of 

 them at the present writing. The most rational thing to do under the circumstances 

 would be to introduce, if possible, a new and neutral nomenclature for the bones of 

 the skull in fishes ; yet I did not think myself justified in introducing such an inno- 

 vation, which at any rate, so long as an exhaustive knowledge of the bones of the 

 skull in fishes is not complete, could only be provisional, and I have therefore con- 

 tented myself with the old names. 



''Bridge, on whose specimen this mesial suture between the ParUalia had worn 

 away, bestows, in consequence, upon the blended bony plates the name of "dcrmo- 

 supraoccipitale," a name which in any event is inadmissible. On seven specimens of 

 Amia, examined by me for the special purpose of looking into this condition, I have 

 invariably found the median suture to be present, agreeing in this particular with the 

 descriptions given by Owen and Franque, and I must consider the condition as found 

 by Bridge as an individual anomaly, to w^hich no further significance need be at- 

 tached. . 



8 Bridge takes this pair of bones for the parietalia because they lie upon either side 

 of his dermosupraoccipitale. 



f'lf Bridge intends to convey the idea that these plates do not meet each other in 

 the middle line, he is m OlTor; his QW^ drfiwing (Plftte XXIII, Fig. 1) proves to tUe 



