Article: Trilobite cuticle microstructure and composition

Previous literature on the microstructure and composition of the trilobite cuticle is reviewed. The micro-structure of the cuticle of Asaphus raniceps Dalman sensu Angelin (1854) is described in detail, and a table outlining the major features of the cuticles of fourteen other trilobite species is included. In Asaphus raniceps and some other species, two main regions of the cuticle are consistently present: an outer layer characterized by perpendicular prisms, representing about one-fifteenth of the total thickness of the cuticle and an inner area forming the bulk of the cuticle. In the inner area of many cuticles, characteristic primary microstructures are fine perpendicular canals, a variety of wider canals, and horizontal laminae. Three types of tubercle are distinguished from thin-sections. Inorganic analyses of Asaphus raniceps show that the cuticle consists largely of calcite. Decalcification of this cuticle with E.D.T.A. left organic residues.