. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. 306 Bashford Dean Memorial Volume Cope, however, did not share Carman's caution. He had not seen Carman's speci- men, nor indeed anything pertaining to the teeth of Chlaynydoselachus, except Carman's figures (identical save for size) in the Bulletin of the Essex Institute (), and in Science (), in which a tooth is represented in three aspects, but so much reduced in si2;e that the minute denticles between the primary cusps are hardly visible under a reading glass. The drawing (the same was used fo
. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. 306 Bashford Dean Memorial Volume Cope, however, did not share Carman's caution. He had not seen Carman's speci- men, nor indeed anything pertaining to the teeth of Chlaynydoselachus, except Carman's figures (identical save for size) in the Bulletin of the Essex Institute (), and in Science (), in which a tooth is represented in three aspects, but so much reduced in si2;e that the minute denticles between the primary cusps are hardly visible under a reading glass. The drawing (the same was used for the figures in both journals) of a tooth may be seen in our Text-figure 1 reproduced in the exact siz;e in which it appeared in Science. Never- theless, Cope, having examined this figure only, proceeded to set forth the following dic- tum (March 7, , p. 276) as to the name and affinities of this shark: The figure of the teeth which he gives shows the animal characterized by Mr. Garman to be a species of the genus Didymodus (Cope) . . equal to Diplodus (Ag.). . , which has hitherto been supposed to be confined to the Carboniferous and Permian periods. The species possesses two, three or four denticles. Material in my possession enables me to fix the position of this genus. . Didymodus becomes by this discovery the oldest living type of vertebrate. To this Carman replied on March 21 (, p. 345) that in Diplodus Ag. the median cone remains rudimentary and the secondary cones are enlarged (as may be seen in our Text-figure 25), while in Chlamydoselachus, as Carman's figure (our Text-figure 10) shows, the median and lateral cones are very large and the secondary ones rudimentary. Carman then suggested that:. calls a "; After Agassiz, 1843. The propriety of placing living species in fossil genera of so long ago on account of resemblances in a single organ, Text-fipure 25 ^'^'"'^ ^^ ^ tooth only of a selachian, is to be questioned. . Two teeth of Dip
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