. A brief general account of fossil fishes : the Triassic fishes of New Jersey. Fishes, Fossil; Paleontology. THE STATE GEOLOGIST. 49 pointed cusps adapted for piercing, and the anterior dorsal fin appears to have been armed with a powerful spine similar to those described under the name of Ctenacanthus. This Devonian genus, as has been said, is the most primitive type of Elasmobranch yet discovered, and is regarded as the ancestral form from which a host of Carboniferous and most modern sharks are derived. A curious form intermediate between sharks and rays (Tamiobatis) is also known from the
. A brief general account of fossil fishes : the Triassic fishes of New Jersey. Fishes, Fossil; Paleontology. THE STATE GEOLOGIST. 49 pointed cusps adapted for piercing, and the anterior dorsal fin appears to have been armed with a powerful spine similar to those described under the name of Ctenacanthus. This Devonian genus, as has been said, is the most primitive type of Elasmobranch yet discovered, and is regarded as the ancestral form from which a host of Carboniferous and most modern sharks are derived. A curious form intermediate between sharks and rays (Tamiobatis) is also known from the Devonian; and if we may assume dental plates to furnish a reliable clue, chimaeroids (Ptyctodus) were present throughout this system in astonishing abundance. During the Carboniferous the group of Elasmobranchs in- creased prodigiously in point of numbers, size and variety, and attained a world-wide distribution, but their rapid culmination which took place at the opening of this era was followed toward its close by an equally notable decline, approaching almost to the verge of extinction during the Permian. Some of the Carbonifer- ous sharks were formidably armed, the largest fin-spines and most powerful crushing, cutting and piercing- teeth known to the science of ichthyology having been developed during this era. An inter- esting generalized shark from the French Coal Measures {Pleura- canthus) combines within itself such a variety of synthetic char- acters as to justify the observation that "it is a form of fish which might with little modification become either a selachian, dipnoan, or ; The long-lived group to which the Port Jackson shark {Cestracion) Fig. 6, belongs was exceedingly plentiful during the Carboniferous, and the number of species very. Port Jackson shark, Cestracion philippi (female). Recent; Australia (From Dean, after Garman.) 4 GEOL XVi. Please note that these images are extracted from scanned page images that may have been digi
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