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Show 1893.] OSTEOLOGY OF LEPIDOTUS AND DAPEDIUS. 565 border of the cranium ; but Bapedius mt least is distinguished Amia and approximated to Lepidosteus by the course of the olfactory nerves across the orbital cavity, while Lepidotus is paralleled only by the last-named genus in the absence of a gular plate. On the other hand, the superficial bones of the two extinct genera differ greatly from those of Lepidosteus and closely resemble those of Amia; the peculiar attachment of the premaxilla in Lepidotus, for example, being reproduced almost in detail in the last-named genus. EXPLANATION OF THE PLATES. PLATE XLIX. Fig. 1. Lepidotus latifrons, sp. nov.; cranial roof, upper aspect, one size. Oxford Clay; Peterborough. [B.M., no. P. 6341.] co., circumorbital; fr., frontal; pa., parietal; sa., squamosal; st., supratemporal. 1 a, b. Basioccipital, lateral and posterior aspects. a, surface of attachment for lateral bones ot cranium ; bc.c, basicranial canal; n.f., notochordal fossa; v., supposed vertebra; x, lateral process. 1 c. Bight premaxilla, showing base of ascending process. Id. Portion of left mandibular ramus, outer aspect. ay., angular; d., dentary. 1 e. Ceratohyal. 2. Ditto ; right maxilla. Ibid. [B.M., no. P. 6838.] 3. Lepidotus minor, Ag.; right premaxilla. Purbeck Formation; Swanage. [B.M., no. 48371.] 4. Lepidotus mantelli, Ag.; transverse section of snout. [B.M., no. P. 6342.] eth., canal through ethmoid bones ; p., palato-pterygoid arcade ; v., vomer. PLATE L. Fig. 1. Lepidotus latifrons. sp. nov.; opercular apparatus of left side, natural size. Oxford Clay ; Peterborough. [B.M., no. P. 6841.] br., branchiostegal ray ; i.op., interoperculum ; op., operculum p.op-, preoperculum; s.op., suboperculum. 2. Ditto; hyomandibular, one half natural size. Ibid. [B.M., no. P. 6840.] p., process for operculum. 3. Bapedius, sp.; cranium from the lateral, posterior (3 a), and anterior (3 b) aspects. Lower Lias; Lyme Begis. [B.M., no. P. 3541.] b.occ, basioccipital; bc.c, basicranial canal; e., ethmoidal region ; /., foramen for olfactory nerve ; m., temporal fossa ; n.f., notochordal fossa ; pfs., parieto-fronto-squamosal shield ; s.occ, supra-occipital. 4. Bapedius granulatus, Ag.; premaxillas (pmx.) and ethmoidal dermal plate (eth.), anterior aspect. Lower Lias; Lyme Begis. [B.M., no. P. 3538.] M. = British Museum. Unless otherwise stated the figures are of the natural size. PROC. ZOOL. Soc-1893, No. XXXVIII. 38 |