. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. 124 Bashford Dean Memorial Volume. Text-figure 10. The dorsal shield of the "Ideal Arthrodire" with bones separated Plates: 17, median-dorsal (MD); 18, antero-dorsal-lateral (ADL); 19, postero-dorso-lateral {PDL); 20, antero-lateral (AL); 21, postero-lateral (PL); 22, spinal (Sp); 23, intero-lateral (IL). Canals: XII, anterior lateral (AsIc); XIII, posterior lateral (Pslc); XIV dorsal (Dc). The nomenclature of the single plates in the carapace ot an Arthrodire is very varied according to the differe
. The Bashford Dean memorial volume : archaic fishes. Fishes; Sharks; Fishes, Fossil. 124 Bashford Dean Memorial Volume. Text-figure 10. The dorsal shield of the "Ideal Arthrodire" with bones separated Plates: 17, median-dorsal (MD); 18, antero-dorsal-lateral (ADL); 19, postero-dorso-lateral {PDL); 20, antero-lateral (AL); 21, postero-lateral (PL); 22, spinal (Sp); 23, intero-lateral (IL). Canals: XII, anterior lateral (AsIc); XIII, posterior lateral (Pslc); XIV dorsal (Dc). The nomenclature of the single plates in the carapace ot an Arthrodire is very varied according to the different writers. In the works of Dean (1901) and Heintz () are found tables giving the names used by various authors. It is usually acknowledged that a mistake is made in calling the different plates in the Arthrodire armor by the same names given to the bones in the cranium and shoulder girdle of the fishes. The Arthrodira are so isolated in theif systematic position that the homology between their carapace plates and the cranial bones of the fishes is too un- certain. Therefore it is better to change such names as "frontal," "parietal," "occipital," "quadratum," "mandible," etc., especially used in Germany by Jaekel, to more neutral names. For this reason, the names given to Arthrodiran plates in England and America are the best. They are based on the position of the plates in the carapace and are there' fore more neutral (, pre-orbital, central, median-dorsal, antero'ventro-lateral, etc.). In 1925, Stensio proposed naming the single plates of the Arthrodiran head with capital letters, as B. M, M2, L, P, etc. This method of nomenclature, notwithstanding its many advantages, is, in my opinion, unsatisfactory. The single letters give no character' istic of the plate's position or relation to other plates, as do the English'American Please note that these images are extracted from scanned page images that may have be
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