. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world. A Lancelet (Atnphioxus). with the skull, and the teeth are united to formbony plates or lamellae. Both groups are veryold in geologic times, having been separated atleast since the Devonian. For this and otherreasons some writers prefer to regard the sharksand chimaeras as separate and coordinategroups. We may without serious violence divide thesharks and rays into six orders; namely, Plcu-ropterygii, Acanthodii, Ichthyotomi, Notidani,Astcro
. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world. A Lancelet (Atnphioxus). with the skull, and the teeth are united to formbony plates or lamellae. Both groups are veryold in geologic times, having been separated atleast since the Devonian. For this and otherreasons some writers prefer to regard the sharksand chimaeras as separate and coordinategroups. We may without serious violence divide thesharks and rays into six orders; namely, Plcu-ropterygii, Acanthodii, Ichthyotomi, Notidani,Astcrospondyli, and Tectospondyli, the firstthree of these being confined to Palaeozoic may regard the Plcuropterygii or the alliesof Cladosclachc as the most primitive, andtherefore as standing first in an ascending series. In this group the pectoral and ventral finsare broad and fold-like, the notoehord is appar-ently not segmented, the tail is short and keeled,well specialized, its tip abruptly turned are no spines, the teeth are small, withmany cusps. There is probably but one family,the Cladoselachida (extinct), Cladosclachcfylc
Size: 3415px × 732px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidamericanauni, bookyear1903
