THE SKELETON IN FISHES. THE SKULL. 123 



with each ramus of the mandible are the dentary, angular, 

 and splenial, in addition to the cartilage bone the articular. 

 Several large opercular bones occur. There are also a pair of 

 large jugular or gular plates, and several large opercular bones. 



In Bony Ganoids both cartilage bone and membrane 

 bone is well developed. The pro-otics and exoccipitals are 

 well ossified, but the supra-occipital and pterotics are not. 

 Lateral ethmoids are developed, and there are ossifications in 

 the sphenoidal region which vary in different 'forms. The 

 place of the cartilaginous palato-pterygo-quadrate is taken by 

 a series of bones, the quadrate behind and the palatine, ecto-, 

 meso- and meta-pterygoids in front. In. Lepidosteus, however, 

 the palatine and pterygoid are membrane bones, as they are 

 in Polypterus and the Frog. Paired maxillae, premaxillae, 

 vomers and a parasphenoid occur forming the upper jaw and 

 roof of the mouth, and a series of membrane bones are found 

 investing the mandible and forming the operculum. 



In Amia 1 membrane bones are as freely developed as they 

 are in Teleosteans ; they include on each side a squamosal, 

 four opercular bones, a lachrymal, a pre-orbital, one or two 

 suborbitals, two large postorbitals and a supratemporal ; while 

 investing the mandible, besides the dentary, splenial, angular, 

 and supra-angular, there is an unpaired jugular. The articular 

 too is double and a mento-meckelian occurs. In Amia teeth 

 are borne on the premaxillae, maxillae, vomers, palatines and 

 pterygoids. 



Bony Ganoids are the lowest animals in which squamosal 

 bones are found, and they do not occur in Teleosteans. 



The suspensoriuin in bony Ganoids, as in the Chondrostei, 

 is hyostylic, and there are two ossifications in the hyoman- 

 dibular cartilage, viz. the hyomandibular, and the symplectic. 



1 T. W. Bridge, "The Cranial Osteology of Amia calva," J. Anat. 

 Physiol. norm. path. 1876, vol. xi. p. 605. K. Shufeldt, "The Osteology 

 of Amia calva," Ann. Rep. of the Commissioner for Fish and Fisheries, 

 Washington, 1885. 



