| The Tremadoc camaroid graptolite (Camaroidea) Tubicamara coriacea Kozlowski, isolated from chert nodules, has been studied using the SEM, LM and TEM techniques. The ectocortex is composed of fibrous fabric, being the sole building material of its supermost and lowermost portions, as well as block of characteristic homegenous material. The latter abounds in the middle portion, where it produces a few layers separated by the fibrous tissue. The preservational corrosion of the upper portion is responsible for the exposure of these blocks seen on the eroded surfaces in the form of characterictic proturberances and tubercles. Such a rough and seemingly sculptured surface is thus secondary, resulting from partial periderm destruction. The origin of condensations of homegenous material within the cortical tissue is discussed in comparison with earlier findings and a description of other ultrastructural features of the studied camaroid is given. |
