The Canadian journal of industry, science and art . exceedingly common occurrence in the Post-Tertiary deposits ofEastern Canada. Fteropoda:—The living pteropods are swimming or floating mol-lusks, frequenting the open sea. Some few are naked, but thegreater number secrete a delicate external shell (univalve,) and allpossess a pair of fins or wing-like appendages for natatory the pteropods with shells, the head is more or less Oonularia is the only form of Canadian occurence, referrible, andthat doubtfully, to this class. Fig. 116 represents0. Trentonensis of the Tre
The Canadian journal of industry, science and art . exceedingly common occurrence in the Post-Tertiary deposits ofEastern Canada. Fteropoda:—The living pteropods are swimming or floating mol-lusks, frequenting the open sea. Some few are naked, but thegreater number secrete a delicate external shell (univalve,) and allpossess a pair of fins or wing-like appendages for natatory the pteropods with shells, the head is more or less Oonularia is the only form of Canadian occurence, referrible, andthat doubtfully, to this class. Fig. 116 represents0. Trentonensis of the Trenton Group. The shell inthis genus is more or less conical and four-angled,furrowed longitudinally, and marked transversely bynumerous straight or zig-zag lines. These latteroften resemble rows of minute punctures. Thegenus extends from the Lower Silurian division intothe Lias formation of the Mesozoic rocks. Fig. iie. Heteeopoda.—The representatives of this class are regarded bymany naturalists as forming simply an Order (Nucleohranchiata) of. MINERALS AND GEOLOGY OF CANADA. 119 the class G-asteeopoda. They constitute however a truly aberrantgroup, having affinities with the Pteropods on the one hand, andwith both Q-asteropods and Cephalopods on the other. Existingforms, like the pteropods, are of pelagic habit, swimming, by meansof a fin-like appendage, in the open seas. The swimming organ is amodification of the gasteropod foot: see below. Some are withouta shell, whilst others secrete one of a fragile and delicate texture.
Size: 1281px × 1951px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1850, bookpublishertoron, bookyear1856
