PEIMOKDIAL PERIOD. 43 



also been obscured by contact with a peculiar accumulation of calcite or 

 arragonite in the form of a layer from two to four millimeters in thickness 

 beneath the whole crust; the crystalline prisms being vertical to the plane 

 of the fossil and also to that of the layer of shale in which it was imbedded. 

 Position and locality. — Shales of the Primordial period, probably of the 

 Potsdam epoch, Antelope Spring, House range, Utah. 



Family ASAPHID^. 



Genus ASAPHISCUS Meek, 1873. 

 Asaphiscus Wheeleri Meek. 



Plate II, fig. 1 a, b, c, d, e, and /. 



Bathyurelhis {Asaphiscus) Wheeleri Meek, 1872, Geol. Surv. Montaua, Idiiho, Wyoiniug, 

 & Utah, 485. 



Body oblong-ovate in outline; sui-face smooth. Head depressed- 

 convex; front margin regularly rounded; postero-lateral angles abniptly 

 rounded, without cheek-spines; exterior margin bent shortly upward all 

 around, producing a raised border of considerable width, and also a rather 

 deep linear depression, or groove, parallel with that border and between it 

 and the remainder of the cheeks. Glabella conical, much wider behind than 

 in front, depressed ; space between its anterior end and the marginal groove 

 about equal to the width of the raised marginal rim in front of it ; outline 

 well defined by the narrow dorsal furrows; sides nearly straight; anterior 

 end abruptly and posterior end broadly rounded, without lateral fuiTOws, or 

 at least they are hardly discernible ; occipital fun-ow shallow, broad, but 

 somewhat distinct and tmiform, extending entirely across the glabella, and 

 continuous with furrows similar to itself that extend to the postero-lateral 

 angles of the head ; the latter furrows lie parallel with and near to the poste- 

 rior margin of the head, giving that margin also a raised border, somewhat 

 like the one upon the exterior margin. Eyes comparatively small, crescentic, 

 situated nearly opposite the mid length of the glabella, and nearly equidistant 

 from it and the posterior margin. 



Thorax having nine segments ; its length not quite so great as that of 

 the head ; axis broadest anteriorly, more strongly convex, and about one- 

 third naiTOwer thaii the lateral lobes are; segments extending straight across 

 the lobe ; lateral lobes depressed, their greatest convexity along the middle ; 



