. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. The postero-ventro'lateral plate shown from the outside. Text-figure 59. Three different median-ventral plates. A, Dmiclithvs terrelh Nwb. (American Museum No. 7304) shown from outside; B, Dimchthys (7) mtermedius Nwb. (Buffalo Museum No. 15608-E2803J from outside. C, Dmchthys (') cunus Nwb. (Ameri can Museum No.'7062) from inside. Antero-Median-Ventral.—This plate (Text-figures 60 and 61 AMV) fills up the cleft between the two antero-ventro-laterals and forms the median strongly curved part of the ventral sh
. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. The postero-ventro'lateral plate shown from the outside. Text-figure 59. Three different median-ventral plates. A, Dmiclithvs terrelh Nwb. (American Museum No. 7304) shown from outside; B, Dimchthys (7) mtermedius Nwb. (Buffalo Museum No. 15608-E2803J from outside. C, Dmchthys (') cunus Nwb. (Ameri can Museum No.'7062) from inside. Antero-Median-Ventral.—This plate (Text-figures 60 and 61 AMV) fills up the cleft between the two antero-ventro-laterals and forms the median strongly curved part of the ventral shield's front margin. It is a small plate with an arched front margin and concave side margins. Broadest in front, it becomes narrow backward, where the side margins run together in a roundish point. On the inside, its fore part is quite deeply impressed; thus the front margin forms a semicircular wall. A T-shaped thickening consolidates the fore part and the median line of the plate (Text-figure 60B t). On the outside AMV is smooth. Its front margin is curved downward, correspond- ing to the front margin of AVL. AMV is slightly overlapped by AVL along the side margin, and its posterior point strongly overlaps the anterior part of M V. In a paper published in 1896, Dean described a ventral shield of Dimchthys terrelli Nwb., noting that in this form the M V and AMV instead of forming two plates, formed only one. In that same year, Eastman pointed out the improbability of this fact. He noted that in all other known forms of Dimchthys, as in all other Arthrodira, these plates are developed as two isolated plates. Later Wright (1897) and Hussakof (1906) mentioned this question. Hussakof conjectured that in primitive forms of Dinichthys AMV and M V were isolated, but that in the more specialized forms these two plates Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of thes
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Keywords: ., book, bookcentury1900, booksubjectfishes, booksubjectfishesfossil
