Further information about this fossil will be eagerly awaited. None of the illustrations so far published shows biramous appendages on the cephalon. This, coupled with the presence of tactile antennæ, makes its reference to the Trilobita impossible, but the present interpretation indicates that it was closely allied to them. [Illustration: Fig. 32. _Marrella splendens_ Walcott. Restoration of the ventral surface, based upon the photographs and descriptions published by Walcott. Although all the limbs of the trunk appear to be biramous, only endopodites are placed on one side and exopodites on the other, for the sake of greater clearness in the illustration. Drawn by Doctor Elvira Wood, under the supervision of the writer. × about 6.] _Restoration of Marrella._ (Text fig. 32.) The accompanying restoration of the ventral surface of _Marrella_ is a tentative one, based on Doctor Walcott's description and figures. The outline is taken from his plate 26, figure 1; the appendages of the head from plate 26, figures 1-3, 5, and plate 25, figures 2, 3; the endopodites, shown on the left side only, from figures 3 and 6, plate 25. I have not studied actual specimens, and the original description is very incomplete. The restoration is therefore subject to revision as the species becomes better known. Arachnida. No attempt will be made to pass in review all of the subclasses of the arachnids. Some of the Merostomata are so obviously trilobite-like that it would seem that their relationship could easily be proved. The task has not yet been satisfactorily accomplished, however, and new information seems only to add to the difficulties. So far as I know, the Araneæ have not previously been compared directly with trilobites, although such treatment consists merely in calling attention to their crustacean affinities, as has often been done. Carpenter's excellent summary (1903, p. 347) of the relationship of the Arachnida to the trilobites may well be quoted at this point: