. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 196 ANATOMY OF VERTEBRATES. underlies the plate d 3, in Acipenser Sturio, so also do the ossified ex- and super-occipitals underlie in PoJypterus the three dermal plates corresponding in position with d 3 in Ac. Sturio. The true par- occipital is equally distinct from the plate marked d 8, in Ac. Sturio and its representative subdivisions in Pohjpterus. The dermal plates in advance of these coalesce with the true parietals, frontals, postfrontals, and part of the mastoids. But the varieties in the dermal plates within th
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 196 ANATOMY OF VERTEBRATES. underlies the plate d 3, in Acipenser Sturio, so also do the ossified ex- and super-occipitals underlie in PoJypterus the three dermal plates corresponding in position with d 3 in Ac. Sturio. The true par- occipital is equally distinct from the plate marked d 8, in Ac. Sturio and its representative subdivisions in Pohjpterus. The dermal plates in advance of these coalesce with the true parietals, frontals, postfrontals, and part of the mastoids. But the varieties in the dermal plates within the limits of a genus, as exemplified by the. 126 Furc rmtf of ciido- .'iiid exo-skeletiiii of Stu sino-le intorfrontal in Acipenser Sturio, by the three interfrontals in Ac. Scypha, by the divided superoccipital plate in Ac. brcviros- tris, &c., sufficiently warn against the confusion arising from applying to dermal plates the names of the true cranial bones in recent and extinct ganoid and placoganoid fishes. The median cranial ganoid plates in the Sturgeons are plainly a continuation forward of the dermal plates, (ib. d s, fig. 125), of the mid-line of the back; and examples of a like re- petition occur amongst the Osseous Fishes in the dermal epicranial spines, for example, of the Angler (Lophius), which suppi5rt the long fishing-fila- ments upon the liead, or in those modified ones forming the sucking disk on the head of the Remora. In certain fishes of the Devonian or Old Red Sandstone ]>eriod the head and part of the trunk were encased by coarticulated ganoid bony jilates. Fig. 127 shows the proportions in which the exo- and endo-skcleton entered into the conservable framework of one of these ancient fishes, termed Coccostei/s (Itdhhos berry, osteon bone), in reference to the tuber- cular enamelling of tlic exterior of the combined helmet and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability -
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1860
