A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) ... / With 7 plates and 96 textfigures.

British Museum (Natural History). Department of Geology

Date:: 1911

Credit: A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) ... / With 7 plates and 96 textfigures. Source: Wellcome Collection.

148/218 page 122

$Gallery VIII. Case A6. Case A5. Wall-case 12a. Gallery VIII. West side and Gallery VII. 122 GUIDE TO THE FOSSIL INVERTEBRATE ANIMALS. # Arctic Ocean was ]>robably cut off l)y a land barrier to the north, while there was free communication with the seas to the south. The Museum possesses the specimens used by Busk in writing his monograjdi on the “ Crag Polyzoa,” and many of them are exhibited. The most interesting forms found in the Crag are some massive Cyclostomes, including the three species known as Alvcolaria semiovata, Fascicularia auranlmm, and F. hibipora. Among the Cheilostomes, the most remarkable forms are two species of Cellana \Sali- cornaria] and one of J^rdiceHta. The numerous species of Sdiizoporclla, Miicrondla, and Membranipora are closely allied to or identical with living forms. A small collection of Pleistocene species from the Clyde and from Selsea Bill is sliown ; but all the.se species still live on the English coast. Tlie Bryozoa from foreign localities are not yet com- pletely arranged, and only a few representative species are exhihited. The lowest slope of the wall-case is devoted to the Palaeozoic faunas, chief of which are those from the Ordovician and Silurian rocks of North America. The Carhoniferous fauna of the same continent furnishes some remarkable forms, notably Ardiiracdes Worthcni, which is like a Fenesfdla twisted into a screw, and Evadmopora qidnqueradiata, another Cryptostome with a star-shaped colony. A collection from the Bathonian deposits of Northern France on the middle slope contains several interesting forms, notably Onydiocdla Jlahdliformis, which is the oldest true Cheilostome known. Among the Tertiary Bryozoa on the top slope, the large specimens from the IMiocene deposits of the Mediterranean are most worthy of notice. The Trustees have published a Catalogue of the Jurassic Bryozoa (1890), and the first two volumes of a Catalogue of the Cretaceous Bryozoa (1899,1909), all by Dr. J. AV. Gregory. lAIOLLUSCA. The.se animals derive their name from their soft bodies {mollis, soft), which never have any internal skeleton, and rarely any hard appendages capable of preservation as fossils. The glandular skin, however, usually secretes, on a portion of the outer surface called the mantle, a hard shell, sometimes horny in appearance, but usually thickened by a deposit of$