. Dura Den : a monograph of the yellow sandstone and its remarkable fossil remains. Sandstone; Paleontology. 62 MONOGRAPH OF DURA DEN. edge, and in exhibiting three well-marked zones, which are smooth in front, and covered with rounded tubercles behind. The most clearly defined distinction in Holoptychius nuhilissimus consists in the size and general roughness of the scales, which are very large on the middle of the belly, and become arched in diminishing gradually towards the tail. In Holoptychius giganteus the scales are very thick, of a rounded form, resting on smooth zones, and beautifully
. Dura Den : a monograph of the yellow sandstone and its remarkable fossil remains. Sandstone; Paleontology. 62 MONOGRAPH OF DURA DEN. edge, and in exhibiting three well-marked zones, which are smooth in front, and covered with rounded tubercles behind. The most clearly defined distinction in Holoptychius nuhilissimus consists in the size and general roughness of the scales, which are very large on the middle of the belly, and become arched in diminishing gradually towards the tail. In Holoptychius giganteus the scales are very thick, of a rounded form, resting on smooth zones, and beautifully ornamented on the inferior side, as in the medullar lines and osseous supports of the Glyptolepis leptopterus. Holoptychius Oma- liusii is distinguished from all the above specific forms in the enormous magnitude and thickness of the scales, which are deeply furrowed, with lon- gitudinal and parallel ridges, which, from their fine irregular granulation, give the appearance of shagreen; and, above all, by the size of a body that must have attained the length of at least twelve feet! This fossil, but very imperfect, has only been found in one locality, namely, in the Old Eed of the neighbourhood of Namur, by M. Omalius de Halloy. The other five species belong to Dura Den and Clashbennie. The specimen on which was determined the species—Holoptychius Ander- soni—was the first discovered of the genus in anything like completeness, and was figui'ed, in 1837, in my Geological and Botanical Description of Fifeshire. The large specimen discovered in 1858, along with the massive caudal fins, on another tablet of rock, completes the entire equipments of this c^lacanthic fossil, showing it in full outline and perspective, and producing as perfect a restoration of a form of extinct life as any in the annals of geo- logical discovery yet recorded. The massive dimensions to which it has attained, and corresponding magnitude of the scales, show a very considerable affinity and resemblance
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Keywords: ., bookcentury1800, bookdecad, booksubjectpaleontology, bookyear1859
