294 FRE.D J. PACK 



extreme ends of the lobes touched. They vary in size and form; in 

 general outline many of them are decidedly hexagonal, others are 

 pentagonal, and still others are nearly circular. The ones nearest 

 the stem do not show the presence of lobes. The lobate plates 

 closely resemble those of the embryonic Antedon. 



The stem is composed of numerous sac-like plates, varying in size 

 and irregularly placed (Fig. i). The diameters of about eight of 

 these appear to equal the circumference of the stem. The stem 

 tapers slightly from the calyx down, and near the lower end turns 

 gently to one side. It is probable that the stem was flexible through- 

 out and possibly prehensile in the lower portion. The extreme tip 

 is not revealed. 



The greatest value of this fossil lies in the stem or pedicle. It is 

 known that some of the primitive cystoids, as Arlstocystis (Barrande, 

 1887), possess no stem whatever. Others, as Dendrocystis (Barrande, 

 1887), have a rudimentary stem, the plates of which are irregular 

 near the calyx, but pass into comparatively large solid plates farther 

 down. In such forms as Trochocystis (Barrande, 1859-87; syn. 

 Trigonocystis, Haeckel) the stem is short and tapering and composed 

 of regularly arranged plates. In the species under discussion the 

 plates composing the calyx, as well as the stem, appear to have been 

 arranged with no regularity whatever. Eocystites? ? longidactylus, 

 therefore, appears to be the earliest form of stemmed cystoid yet 

 described. 



Location and formation: Two miles west of Pioche at the Abe 

 Lincoln Mine, on the southwest slope of the mountains, in a pinkish 

 shale of Mid- Cambric age. 



PTEROPODA 



GENUS HYOLITHES, Eichwald 



HYOLiTHES,Eichwald, 1840: Sil. schicht. Syst. in EhstL, p. gy. 



Hyolithes billingsi, Walcott 



S'lUerella obtusa, Billings, 1861: Geology oj Vermont, Vol. II, p. 955. 



H yoUthes primoirdialis ? White, 1874: Geographical and Geological Explora- 

 tion and Survey, West of the looth Meridian, Preliminary Report, Invertebrate 

 Fossils, p. 6. 



Hyolithes billingsi, Wallcott, 1886: Bulletin No. 30, U. S. Geological Survey, 

 p. 134, Plate 13. 



