The individual portions of which the limbs are made up are called segments, and the articulations between them, joints. Such a procedure is unusual, but promotes clearness.
The first mention of Neolenus with appendages preserved was in Doctor Walcott's paper of 1911, in which two figures were given to show the form of the exopodites in comparison with the branchiæ of the eurypterid-like Sidneyia. In 1912, two more figures were presented, showing the antennules, exopodites, and cerci. The specimens were found in the Burgess shale (Middle Cambrian) near Field, in British Columbia. This shale is exceedingly fine-grained, and has yielded a very large fauna of beautifully preserved fossils, either unknown or extraordinarily rare elsewhere. It was stated in this paper (1912 A) that trilobites, with the exception of Agnostus and Microdiscus, were not abundant in the shale.
In discussing the origin of the tracks known as Protichnites, Walcott presented four figures of Neolenus with appendages, and described the three claw-like spines at the tip of each endopodite.
Three new figures of the appendages were also contributed to the second edition of the Eastman-Zittel "Text-book of Paleontology" (1913, p. 701). Later (1916, pl. 9) there was published a photograph of a wonderful slab, bearing on its surface numerous Middle Cambrian Crustacea. Several of the specimens of Neolenus showed appendages.
Finally, in 1918, appeared the "Appendages of Trilobites," in which the limbs of Neolenus were fully described and figured (p. 126), and a restoration presented. Organs previously unknown in trilobites, epipodites and exites, attached to the coxopodites, were found.