File:A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) (1907) (14776295601).jpg

Identifier: guidetofossilinv00brit (find matches)
Title: A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history)
Year: 1907 (1900s)
Authors: British Museum (Natural History). Dept. of Geology Bather, Francis Arthur, 1863-
Subjects: Fossils
Publisher: London, Printed by order of the Trustees
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
Fig. 90.—Fourlobed aperture. upper paired openings. Some allied 160 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. Gallery forms had a larger number of paired openings and could,VII. one supposes, stretch out more arms (Fig. 90). Ascoceras, ATall-case ^j^ich occurs in the Ordovician of North America and theSilurian of Europe, especially Bohemia, had a curious life-history. This may be followed in the enlarged and dia-grammatically coloured model which is exhibited. Beginningwith a narrow tubular shell, divided by transverse septa, andhaving a simple siphuncle near the margin (Fig. 91 F), itsuddenly swelled out like a Poterioceras. This gave more
Text Appearing After Image:
Fig. 91.—Ascoceratidse. A, upper part of shell of Ascoceras manubrium,cut down the middle, showing the upward-curved septa on the left;B, C, D, large curved septa of Ascoceras fistula ; E, upper part of shellof Ascoceras decipiens, with septa of ordinary type formed after thedeposition of the upward-curved septa ; F, the shell of the same speciescompleted, showing the simple nautiloid portion (n); G, H, fragmentsof an allied form, Choanoceras. (From Foord, after Lindstrom.) room for the visceral cone with its contained genital^glands,and naturally changed the character of the septation (Fig. 91A, F). The body now had so much room that it ceased toadvance to any great extent. On the contrary, as the animalgrew older its body contracted, and first the opening ofthe body-chamber narrowed somewhat. Then the visceralhump shrank a little at its end, but more at the side, muchas it did in the early stages of JSndoceras. Thus the septanow produced remained close together at the apex of theb

Note About Images