A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . yolithes [Theca ] and a few similarforms is composed of carbonate of lime, is conical, straight,or curved, triangular, elliptical, or flattened in cross surface is smooth or striated, and it is closed by anoperculum. The narrow end of the shell is often divided bycross partitions. Species of this genus lived throughout thePalaeozoic Era, but were most abundant in its earlier shell of Tentcmdites is an elongate cone, ornamentedwith rings. It of
A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . yolithes [Theca ] and a few similarforms is composed of carbonate of lime, is conical, straight,or curved, triangular, elliptical, or flattened in cross surface is smooth or striated, and it is closed by anoperculum. The narrow end of the shell is often divided bycross partitions. Species of this genus lived throughout thePalaeozoic Era, but were most abundant in its earlier shell of Tentcmdites is an elongate cone, ornamentedwith rings. It often begins in a small bulb, and the earlierportion may be partitioned as in Hyolithes. Its thick wall iscomposed of two layers. The genus abounds in Silurian andDevonian rocks, oftenbeing the chief consti-tuent of certain is the mostwidely distributed inspace and time, and con-tains the greatest numberof species and the largestindividuals of all Conu-larida. The shell is elon-gate and four-sided. Eachface is divided lengthwiseby a groove (Fig. 76 c) and ornamented with parallel ridges, which slope upwards toward. a h c Fig. 76.—Conularia qitadrisidcata, CoalMeasures of Coalbrookdale. The lowerend is broken off. a, side view; b,aperture seen from above ; c, back view. 142 GUIDE TO THE FOSSIL INVERTEBEATE ANIMALS. G-alleryVIII. Wall-cases8&9. Wall-case9c. Wall-case9. Wall-case8. Wall-cases ;, top slope. Wall-case8. Wall-case7. this groove. The margin of the shell opening is folded in-wards (Fig. 76 6). A few specimens of Cambrian age areshown. The largest are Ordovician, those from the Gres deMay in Calvados being noteworthy. Several species occurin Silurian rocks, and there will be noticed some specimenswell preserved in nodules from the British Coal from the Permo-Carboniferous rocks of Eew SouthWales are exhibited, A single species is also found in theTrias and in the Lias. We return now up the side of the Gallery, taking the Wall-ca
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