634 ME. W. G. RIDEWOOD OS THE [NOV. 6, 



Ganoid fishes and Rays, the application of this name needs no 

 further support. 



The term basihyal is here applied to the median conical cartilage 

 in preference to Giinther's original name glossohyal, because the 

 cartilage is a ventral copula, corresponding in all essential respects 

 with the basihyal of the Sharks, and it is with the Elasmobranch 

 and Ganoid, rather than with the Teleostean fishes, that com- 

 parisons should be instituted. 



The chief feature of interest in connection with these three 

 anterior cartilages is the contact of the hypohyals in the median 

 plane, in addition to their articulation with the basihval. 



Briihl (2) (Taf Ixi. Fig. 1) follows Giinther in calling the 

 hypohyal the basihyal, but in another place (Taf lxvii. Fig. ]) he 

 describes it as the epiphysis of the ceratohyal '. This, in addition 

 to being an inconsistency, is an error, since there is a cartilaginous 

 epiphysis to the ceratohyal in addition to the hypohyal cartilage 

 in question, assuming even then that the term epiphysis may be 

 employed in describing the skeleton of animals other than 

 mammals. 



Briihl also claims to have discovered a small median urohyal, 

 projecting back from the hypohyals and lying between the anterior 

 end* of the ceratohyals. There is certainly a small rod of cartilage 

 in this situation, but, from its position between the lower ends of 

 the first ceratobranchials, it is more reasonable to regard it as a 

 basibrancbial than as a constituent of the hyoid arch. 



On comparing the hyoid arch of Ceratodus with that of a Shark, 

 but little doubt can be entertained as to the homology existing 

 between the elements called in each case the ceratohyal ; the 

 proportionate size, position, and the relations to the hyoid demi- 

 branchia and to the mandibular and branchial arches, the nature 

 of the ligamentous attachment to the mandible (seen better in 

 Protoptems than in Ceratodus), all point to this conclusion. So 

 that, arguing along these lines, the small cartilage (hm, fig. 2) 

 closely bound to the cranial cartilage, if an element of the hyoid 

 arch at all, is a much reduced representative of the well-developed 

 and functional hyomandibular of the Shark, a view first propounded 

 by Huxley (5), and which has not been challenged except by 

 Briihl (2), who proposes to call this cartilage the "stylhyale," 

 without, however, giving his reasons for the change. 



Van Wijhe (12) accepts Huxley's determination, but in a foot- 

 note remarks : — " Es scheint mir jedoch nicht unmoglich, dass 

 dieses Knorpelstiick ein Interhyale repriisentire."' 



In a revolutionary paper by Pollard (10), this cartilage is 

 regarded as an opercular. This author, however, elects to compare 

 the skull of Ceratodus with that of the Siluroids, which are by no 

 means the most typical nor the most primitive of the Teleostei ; 



1 Briihl calls the ceratohyal the epihyal, and is supported by so recent a 

 writer as Teller (11). 



