Figure 49.3: A typical trilobite. This is a fossil specimen of the speciesElrathia kingii, and is 4.2 cm long.
(Credit: http://www.fossilmuseum.net.))
Figure 49.4: Descartes’ lens design for minimal aberration (above left) is found in the lens of the trilobite
Crozonaspis(right). Light ray paths entering the lens from the left come into focus a short distance to the right
of the lens (blue). In the eye ofCrozonaspis, an intralensar body (white) further corrects focus after passing
through the outer lens layer (blue).(Credit: “A Guide to the Orders of Trilobites,” http://www.trilobites.info. Image
copyright ©1999, 2000 by S.M. Gon III, modified from Clarkson and Levi-Setti, 1975.)
Figure 49.5: Huygens’ lens design for minimal aberration (above left) is found in the lens of the trilobite
Dalmanitina(right).(Credit: “A Guide to the Orders of Trilobites,” http://www.trilobites.info. Image copyright
©1999, 2000 by S.M. Gon III, modified from Clarkson and Levi-Setti, 1975.)