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This scientific drawing illustrates the central section of a graptolite colony recovered from the Upper Llandeilo strata of Dumfriesshire. The specimen is characterized by two slender, diverging branches that extend outward from a central point, forming a wide, V-shaped configuration. Along the inner margin of each branch, a continuous row of small, serrated projections represents the thecae, the individual chambers that once housed the living members of the colony. At the base of the divergence, three sharp, needle-like spines are visible, which likely served as structural supports or attachment points for the organism. This particular form of colonial marine life is a key diagnostic fossil used by geologists to identify and date sedimentary rock layers from the Lower Silurian period.