. The annals and magazine of natural history : zoology, botany, and geology . It is interesting to note that in the Devonian genus Cheirolepis theventral tin is longer than the anal. Fhylogeny of the Teleostomi. 335 the overlying cleithrum must be regarded as typical of theancestral Teleostome; whether the fusion of the posterioraxonosts also is corelated with this, or whether the meta-pterygium was represented in the early Teleostomi by a seriesof separate axonosts, there is no evidence to show, but thestructure of the pectoral in all Teleostomi is easily explicableas a modification of that o
. The annals and magazine of natural history : zoology, botany, and geology . It is interesting to note that in the Devonian genus Cheirolepis theventral tin is longer than the anal. Fhylogeny of the Teleostomi. 335 the overlying cleithrum must be regarded as typical of theancestral Teleostome; whether the fusion of the posterioraxonosts also is corelated with this, or whether the meta-pterygium was represented in the early Teleostomi by a seriesof separate axonosts, there is no evidence to show, but thestructure of the pectoral in all Teleostomi is easily explicableas a modification of that of Psephurus. In the structure of their median, as well as of the pairedfins, the Chondrostei are essentially primitive, and the con-dition of the vertebral column also bears witness to their lowposition. It appears to me fairly well established for bothliving forms and for those extinct ones which undoubtedlybelong to this order that the hyomandibular does not developa posterior process for articulation with the inner face of theoperculum, as is the case in all Fig. 1.—Diagrams to show the arrangement of the hranchiostegals andgular plates in a t}rpical Crossopterygian, Chondrostean, andTelecst. A. Rhizodopsis sauroides (after Traquair) ; B. Bhabdu-lepis macroptertts (alter Traquair); C. Amia calm. , inter-gular; y., gular plates; iff., lateral gulars ; b., cerato-hyal; , suboperculum ; mn., lower jaw. In the Palteoniscidse the arrangement of the plates supportingthe gill-membranes and extending forward between the man-dibular rami, as described by Traquair *, is one from which theconditions which obtain in other Teleostomi are readily deriv-able. On each side there is a continuous series of obviouslyhomologous plates, the upper two or three of which are en-larged as the opercular bones, those following being thebran- * Mon. Falaeont. Soc, Paheoniscidne, p. 21 (1877). 336 Mr. C. T. Began on the chiostegals, the anterior pair of which
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