The individual segments of the endopodites can not be seen clearly enough to make any measurements. On the fourth and fifth endopodites of the thorax, some of the segments seem to be broad and triangular as in Triarthrus. All that can be seen indicates that Acidaspis had appendages entirely similar to those of Triarthrus, but perhaps not quite so long, as they seem not to have projected beyond the limits of the lateral spines. There are no traces of antennules nor, unfortunately, of exopodites.
Measurements: Length 8 mm.
Walcott (1881, p. 206) stated that his sections had shown the presence in this species of legs "both cephalic and thoracic" and also the "spiral branchiæ." His specimens were from the Trenton at Trenton Falls, New York.
The Appendages of Cryptolithus.
Cryptolithus tessellatus Green.
([pl. 6, fig. 7]; pls. [7]-[9]; text figs. [20], [25], [45], [46].)
(See also [Part IV].)
Illustrated: Beecher, Amer. Jour. Sci., vol. 49, 1895, pl. 3.
When Professor Beecher wrote his short article on the "Structure and Appendages of Trinucleus" (1895), he had only three specimens showing appendages. In his later work he cleaned several more, so that there are now thirteen specimens of Trinucleus = Cryptolithus available for study, though some of these do not show much detail. In his last and unpublished study, Beecher devoted the major part of his attention to this genus, and summarized his findings in the drawings which he himself made of the best individuals (text figs. [45], [46]). Valiant (1901) stated that he had found a Trinucleus with antennæ in the Frankfort shale south of Rome, New York. The specimen has not been figured.