[55] THE OSTEOLOGY OF AMIA CALVA. 801 



its straight border articulates in an elongated facet in the cartilage 

 over the otic region. Behind, it supports a large circular facet, borne 

 upon a subsessile stem, for the operculum {ro). 



Its relation with the cartilaginous iuterhyal and the symplectic 

 agrees very closely with typical Teleosteans. 



Bridge seems to be inclined to believe that the angle formed anteri- 

 orly by the long axes of hyomaudibular and symplectic, which give these 

 bones their directions, may account for the movement forward of the 

 metapterygoid in this Ganoid. In most Teleosteans this latter bone is 

 directly over the quadrate, and not in front of it. In this I cannot 

 agree with him, but attribute the position of the metapterygoid in 

 Amia, entirely to its unusual size, as compared with the neighboring 

 bones, rendering it a physical impossibility to assume any other posi- 

 tion. This bone in a bass {Micropterus salmoides) before me is squarely 

 over the quadrate and rather behind it, whereas the anterior angle 

 formed by the hyomandibular and symplectic is quite as acute as it is 

 in Amia, but the quadrate is relatively very much smaller. 



Of the hyoidean and branchial arches (Fig. 19). — In this connection 

 I will also describe the extraordinary series of branchiostegal rays in 

 Amia.^^ There are twelve of these appendages, articulating through 

 ligamentous attachment, well within the posterior borders of the epihyal 

 and ceratohyal, upon their outer surfaces. They diminish gradually 

 in size from above downward, slightly overlapping each other about 

 half way down the series. The superior and largest has a somewhat dif- 

 ferent form from the others, being a long ellipse, with a well-marked 

 longitudinal groove close to its upper border on its external aspect. 

 This surface likewise is sculptured all over quite as thoroughly as one 

 of the ganoid plates and in a similar manner. It articulates both with 

 the epihyal and ceratohyal. The sculpturing gradually disappears as we 

 near the middle of the series, through it can be faintly discerned to the 

 very anterior ray. In life, these rays lap each other anteriorly, the set 

 from one side over the set from the other, under the throat, where they 

 constitute a striking feature and unique ornament. 



The articulation of the hyoid with the hyomandibular and sym- 

 plectic, through the intervention of the cartilaginous interhyal with this 

 bone and the epihyal is very similar to the state of affairs as we find it 

 among ordinary teleostean fishes. Holding a mid-position in the arch, 

 the ceratohyal is a. strong, well developed bone, bent at an elbow 

 near its middle (Fig. 19 c. hy). The arch is completed by the lumpy 

 little hypohyal, borne at its anterior extremity {H. hy). ]N"o evidences 

 exist of an ossified glosso-hyal. 



The basibranchial elements of the branchial apparatus are composed 

 chiefly of cartilage with very' little bone ; one of the number seems to be 



62 Mr. Bridge seems to have unfortunately secured an imperfect specimen of the mud- 

 fish in this particular, as he affirms that there are but eleven of these rays, that is 

 hardly a good reason, however, for figuring but <e».—( Jour, of Anat., July, 1877, p. 

 609, and Fig. 6, Plate IV.) 



H. Mis. 67 51 



