. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Phylogeny of tlie TeJeostomi, 337 changed, but tlie metapterygium became segmented (or tliis segmentation may be primitive, each segment representing an axonost). From such an asymmetrical fin the symmetrical fins of Geratodus would be derived by an increase in length of the lobe and of the number of axial segments and the development of posterior cartilages for the support of the inner series of dermal rays. The evolution of the ventral fins would be on similar lines. :)^ >
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Phylogeny of tlie TeJeostomi, 337 changed, but tlie metapterygium became segmented (or tliis segmentation may be primitive, each segment representing an axonost). From such an asymmetrical fin the symmetrical fins of Geratodus would be derived by an increase in length of the lobe and of the number of axial segments and the development of posterior cartilages for the support of the inner series of dermal rays. The evolution of the ventral fins would be on similar lines. :)^ >?. Fig-. 2.—Diagrams to illustrate the evolution of lobatc paired fins ; the axonosts are unshaded, the baseosts shaded 1, jminitive con- dition ; 2 and 3, sta;ies seen respectively in ventral and pectoral of Acipenser ; 4, obtusely lobate fin; 5, pectoral of Folypterus; 6, acutely lobate fin. In the pectoral tin of Poh/pterus there are two basal pieces articulated to the coraco-scapular ossifications, which Traiiuair (Tr. R. Soc. Edin. xxvii. 1876, p. 383, pi. xxxii. fig-. 9), would seem to consist of an axis (nietapteryrriunij of three segments an I of three baseosts, of which the first appears to be attached to the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original London, Taylor and Francis, Ltd
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