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Show 1896.] PISHES OF THE FAMILY GONOEHYNCHID.E. 501 became the type of the genus Sphenolepis of Agassiz l, and was then referred to the Esocidae. The Montmartre specimen described and figured by Cuvier was also placed in the same genus under the name of Sphenolepis cuvieri; and since that date both these fishes seem to have been always quoted as related to the genus Esox. A recent examination of the specimens of these two fishes in the British Museum has now convinced the present writer that Cuvier's original comparison of Sphenolepis cuvieri with Gonorhynchus was correct; that Sphenolepis squamosseus certainly belongs to the same genus; and that both these fishes are generically identical with Notogoneus osculus from the freshwater Green Biver Shales (Eocene) of Wyoming, U.S.A., which Professor Cope referred to the Gonorhynchidae eleven years ago2. As the only surviving genus, Gonorhynchus, seems to be exclusively restricted to the seas bordering Japan, South Africa, Australia, and N e w Zealand, the discovery of an extinct freshwater ally both in Europe and America is one of some interest. It is thus important that the principal osteological characters of the known fossils should be clearly stated to justify the comparisons made. 1. NOTOOOSTEUS OSCULTJS. (Plate XVIII. figs. 1, 2.) 1885-86. Notogoneus osculus, E. D. Cope, Amer. Nat. vol. xix. p. 1091; Mem. Nat. Acad. Sci. vol. iii. p. 163, pl. with figs. 4, 5. Formation and Locality. Green Biver Shales (Eocene); Wyoming, U.S.A. The North-American form Notogoneus osculus has already been well described by Cope, who also publishes a diagrammatic figure. A beautiful new specimen, however, lately acquired by the British Museum, permits the determination of a few additional features. The head in this fossil, shown of the natural size in Pl. XVIII. fig. 1, is exposed directly from the side, and thus does not exhibit the hinder part of the cranial roof, which is fortunately well seen in the original specimen figured by Cope. The large and characteristic right frontal bone (fr.) is distinct, while the upper part of the otic region (ot.) is shown to be well ossified, and is evidently not entirely covered by the squamosal. The much-expanded hyoman-dibular (hm.) is exposed, except at its lower end; but the other elements of the suspensorium, as also those of the pterygo-palatine arcade, are too much crushed and fractured to be distinguishable. The articulation for the mandible, however, is distinct below the front border of the orbit, and portions of both rami are preserved, that of the left side thrown upwards a little above the right ramus. Though imperfect the bones here indicated can readily be determined by reference to the corresponding elements in the existing Gonorhynchus (Pl. XVIII. fig. 5). The articulo-angular bone (ag.) is almost fan-shaped, extending upwards immediately in front of the articulation into a large, bluntly-pointed process. The dentary (d.) is much larger than the latter element, truncated in front, with very short oral border, and rising into au enormous upwardly- 1 Poiss. Foss. vol. v. pt. ii. (1844), p. 87. 2 American Naturalist, vol. xix. (1885), p. 1091. |
