. The elasmobranch fishes. Chondrichthyes. Fig. 19. Fig. 21 Fig. 20 Fig. 19. Pristis cuspidatum. (From Garman.) Fig. 20. Baia erinacea. (From Garman.) Fig. 21. Disceus thayeri. (From Garman.) it the pectoral fins meet in front and behind so that tlie body is essentially disc-shaped. Like other rays of this type its tail is provided with a serrate sting, but unlike TJrolophus the tail is whip-like and has but slight indication of fins or folds. External Form ix Its Development The transition in external form which we have just considered in the series of sharks and rays may be similarly followe
. The elasmobranch fishes. Chondrichthyes. Fig. 19. Fig. 21 Fig. 20 Fig. 19. Pristis cuspidatum. (From Garman.) Fig. 20. Baia erinacea. (From Garman.) Fig. 21. Disceus thayeri. (From Garman.) it the pectoral fins meet in front and behind so that tlie body is essentially disc-shaped. Like other rays of this type its tail is provided with a serrate sting, but unlike TJrolophus the tail is whip-like and has but slight indication of fins or folds. External Form ix Its Development The transition in external form which we have just considered in the series of sharks and rays may be similarly followed in a series of stages in the life- history of an individual ray. In other words, while a ray and a shark are very dissimilar in the adult, they are much alike in their earlier development. As growth proceeds, the ray gradually diverges from the shark-plan so that finally a fixed gulf separates the two. To illustrate this divergence we may again compare Acmithias and 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 Daniel, J. Frank (John Franklin), 1873-1942. Berkeley,Calif. , University of California press
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