A treatise on zoology . l; o, orbit; op, opercular ; pop, preopercuiar ,pt, pterygoid ; n, quadrate ; sop, subnpercular ; .--p, splenial. Eurynotiis, Ag. ; Mesolepis, Young (Fig. 290); WardicMliys, Traq.;Cheirodus, :\ICoy; Cheirodopsis, Traq. ; Carboniferous, Great , Miinster ; Permian, Europe. Platysomus, Ag. ; Carboniferousand Permian, Europe. Family Catopteridae. A triassic family of fusiform fish resembling-the Palaeoniscidae in general structure ; but with an abbreviate hetero-cercal tail, and lepidotrichia which only slightly exceed the radials innumber. The latter also
A treatise on zoology . l; o, orbit; op, opercular ; pop, preopercuiar ,pt, pterygoid ; n, quadrate ; sop, subnpercular ; .--p, splenial. Eurynotiis, Ag. ; Mesolepis, Young (Fig. 290); WardicMliys, Traq.;Cheirodus, :\ICoy; Cheirodopsis, Traq. ; Carboniferous, Great , Miinster ; Permian, Europe. Platysomus, Ag. ; Carboniferousand Permian, Europe. Family Catopteridae. A triassic family of fusiform fish resembling-the Palaeoniscidae in general structure ; but with an abbreviate hetero-cercal tail, and lepidotrichia which only slightly exceed the radials innumber. The latter also appear to be formed chiefly of one longproximal segment. In the characters just mentioned the Catopteridaenndoubtedly approach the Holostei, with which they should possibly beclassified. The head and shoulder girdle are quite Palaeoniscid. Theganoid scales are rhombic; the teeth slender and conical [505]. Catopterus, Eedf. ; Trias, N. America. Dictyopyge, Eg. (Fig. 292);Trias, N. America and Europe. 314 PALAEONISCOIDEI. A CIPENSEROIDEf 315 Sub-Order 2. ACIPENSEROIDEI. According to the researches of Traciuair [-i)!] and A. [505], the families in this group form a degeneratingseries starting from a type simihir to the Palaeoniscids ; they reachtlie highest degree of differentiation in tlie Acipenscrichie. The body remains fusiform with a typical bifurcated hetero-cercal tail. The dorsal and anal fins are moderately short. Theorbits are far forward, near the olfactory capsules, but the snoutbecomes greatly prolonged lieyond them and the mouth. This rostrum is borne by a prolongation of the median ethmoidcartilage (Fig. iOo). The cartilaginous cranium is, indeed, in livingforms massively developed, and extends far bnclc, passing gradually
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