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Show 634 MR. W. G. RIPEWOOD ON 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 comparisons 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 basihyal. Briibl (2) (Taf lxi. Fig. 1) follows Giinther in calling the hypohyal the basihyal, but in another place (Taf lxvii. Fig. 1) he describes it as the epiphysis of the ceratohyall. 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. Briibl also claims to have discovered a small median urohyal, projecting back from the hypohyals and lying between the anterior ends 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 basibranchial than as a constituent of the hyoid arch. O n 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 denii-branchia and to the mandibular and branchial arches, the nature of the ligamentous attachment to the mandible (seen better in Protopterus 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), w h o 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 footnote remarks :-" Es scheint mir jedoch nicht unmoglich, dass dieses Knorpelstiick ein Interhyale reprasentire." 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 writer as Teller (11). |