. Annual report of the Regents. New York State Museum; Science. 88 NEW YORK STATE MUSEUM the triliobite stock and differentiation therefrom at a very early period of geologic history. The genus A g 1 a s p i s Hall, described as a trilobite from the Cambric (upper) of Wisconsin, was, in Eastman's edition of Zittel's Texthook of paleontology, removed by the writer from the trilobites and placed under the family Aglaspidae of the order Synxiphosura Paekard, in immediate association with the Hemi- aspidae (1899, p. 672). Aglaspis eatoni Whitfield^ a figure of which is here reproduced, has a lobed
. Annual report of the Regents. New York State Museum; Science. 88 NEW YORK STATE MUSEUM the triliobite stock and differentiation therefrom at a very early period of geologic history. The genus A g 1 a s p i s Hall, described as a trilobite from the Cambric (upper) of Wisconsin, was, in Eastman's edition of Zittel's Texthook of paleontology, removed by the writer from the trilobites and placed under the family Aglaspidae of the order Synxiphosura Paekard, in immediate association with the Hemi- aspidae (1899, p. 672). Aglaspis eatoni Whitfield^ a figure of which is here reproduced, has a lobed head-shield, low, conate central area, approximate and small compound eyes and no facial sutures. Its abdominal seg- ments are flat and blade-like, markedly simi- lar to those of Pseudoniscus, and the body ends in a similar telson spine. Its seg- ments have been reported as seven in number. It clearly represents an early stage of the stock to which the hemiaspids belong, nearer to the Aglaspis eat on Whitfield ,.,,., , ^ Upper Cambric, Lodi Wis. point of departure from the trilobite stock, and yet it may be said that the slight difference in the expression of the type after the long interval from Cambric to late Siluric shows its stability. With the evidence afforded by these recent acquisitions of Pseudoniscus we may submit the following diagnosis of the genus: Pseudoniscus Nieszkowski 1859. Animal small. Head- shield relatively large, convex; eyeless; no facial sutures; genal angles extended into short spines; surface very obscurely marked by radial furrows (impressions of appendages?). Abdomen strongly trilobed and trilobitiform. Segments 10, flat, smooth; those of the preabdomen 1-5 with o'bliquely grooved pleux^ae; sixth and seventh segments partially conjoined on the pleurae; segments of postabdomen narrow, lanceolate and with increasing retral cur- vature. Telson a simple shor-t, straight Please note that these images are extracted from scanned page images that
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