. A history of British fossil mammals, and birds . r to it; and the section ofthis dark-coloured dentinal pith (fig. 227, cl)^ at eachend of the fragment, would alone have prevented any onecognizant of the form and Fui. 2-27. structure of the Cachalotstooth, from mistaking thefossil for a tooth of thatrecent Cetacean. The mi-croscopic structure of theFelixstow fossil shows itsnear aflSnity to the Physeter^but at the same time provesits specific distinction. The dentinal axis, (, c/,) is finely grooved longitudinally ; the margin ofits transverse section appearing crenate under a low mag
. A history of British fossil mammals, and birds . r to it; and the section ofthis dark-coloured dentinal pith (fig. 227, cl)^ at eachend of the fragment, would alone have prevented any onecognizant of the form and Fui. 2-27. structure of the Cachalotstooth, from mistaking thefossil for a tooth of thatrecent Cetacean. The mi-croscopic structure of theFelixstow fossil shows itsnear aflSnity to the Physeter^but at the same time provesits specific distinction. The dentinal axis, (, c/,) is finely grooved longitudinally ; the margin ofits transverse section appearing crenate under a low mag-nifying power. Viewed under a higher one by light trans-mitted through a thin slice (fig. 228), its substance is seento be traversed by dentinal tubes radiating from the centreto the circumference, in a plane more transverse to the axisthan in the Cachalots dentine. The tubes present anaverage diameter of fs^o^th of an inch, with interspacesof about twice that diameter: they are thus more closelypacked than in the Cachalot. They are minutely un-. Transverse section of fossil tooth ofBalBenodoii, Red-Crag. Nat size. 538 BAL^NODON. dulated, divide and subdivide dicliotomously in theircourse to the periphery of the axis, where they terminatein very fine irregularly Lent ramuli; some forming loops,others dilating into minute calcigerous cells. The den- Fiy. 228. :^^w^ V C f-^r. lt;Mi\iJ^\
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Keywords: ., bookaut, bookcentury1800, bookdecade1840, booksubjectpaleontology
