Thesaurus siluricus : the flora and fauna of the Silurian period : with addenda (from recent acquistions) / by John J. Bigsby.

Date:
1868
Catalogue details

Licence: Public Domain Mark

Credit: Thesaurus siluricus : the flora and fauna of the Silurian period : with addenda (from recent acquistions) / by John J. Bigsby. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    Table C.—Progress in British Gasteropoda. Primordial. Llandeilo. Caradoe. Wenlock. Lower Ludlow. Upper Ludlow. T3 ? s> bp j: •ji a Total. 2 7 34 35 17 23 10 2 130 We here begin and end with two species, or more truly with four different species ; but the majority of the Gasteropoda are about the middle of the mass of beds, as is usual. The Llandovery beds become rich by borrowing six species from the lower stage. The names of the species referred to in the above Table can be had by reference to Murchison's ' Siluria,' 4th edition, pp. 531 &c. In so extraordinarily rich a district as Central Bohemia it is worthy of notice that out of the whole fifty-one genera of this order it has only twenty-three, and these are poor in species. It is, however, the richest area of all, England coming next, with twenty genera; one only in common, Acroculia. The interesting Table D, here subjoined, exhibits the proportions in which the species of the Gasteropoda are found in the four stages of the Silurian epoch, according to our present knowledgf. Table D. Genera. Acroculia .. Calyptrsea ... Carinaropsis CeritIlium ... Chemnitzia Chiton Cirrus Cleodora .. Clioderma ... Clisiospira ... Cyclonema... Delphinula? . Dentalium Eunema Euoniphalus . Gyrotrema Helicotoma . Holopa;a .... 3 I 12 21 11 22 110 106 Genera. 197 Brought forward Holopella Hormotoma .. Litorina Loxonema Macrocheilus.. Metoptoma .. Murcliisonia ... Natica Naticella Ophileta Patella Pliasianella ... Pilidion Platyohisma ... Platyostoma ... Pleurotomaria Porcellia 12 32 102 110 5 2 1 2 2 15 51 5 1 5 6 1 280 25 1 1 14 1? 197 7 1 23 3 31 15 4 Genera. 74 356 Brought forward Raphistoma .. Rotella Seal ites Scoliostonia .. Siplionaria Stomatella Straparollina... Straparollus ... Strophostylus Subulites Ti-ochonema ... Trochus Tubina Turbo Turritella Vermetus ? Total 102 3 280 14 113 329 85 356 430 There are several things worthy of notice in this Time-table of the Gasteropoda. The species augment with the progress of the epoch, those of the upper stage being nearly four times as many as the Primordial. The poverty observed in the Middle Silurian is due to well-known circumstances, and is incident to almost all areas. We have in the Primordial stage 121 appearances, which are, except eight, all distinct species. Only one of these species passes into a higher stage, the Pleurotomaria Proyne (also of Black-River and Trenton Limestones). The genera in the four stages we have adopted are in number 19, 17, 3, and 12 respectively; and the species, taken in like succession, are 113, 329, 85, and 430. C
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