40 LOWER CAMBRIAN FOSSILS— WALCOTT. 



Formation and locality.— In the upper portion of the Lower Cam- 

 brian rocks, a short distance northeast of Saleoi, Washington County, 

 New York. 



Nat. Mus. Cat. Invt. Foss., No. 18327. 



Agnostus sp. ? 



This species is represented by two imperfect heads of the type of 

 Agnostus fallax Linnarsson, of the Middle Cambrian of Sweden, or A. 

 acadicus Hartt, of New Brunswick. It is found at the same locality 

 with A. desideratus and also two miles south- southeast of Granville, in 

 Washington County, New York. 



Nat. Mus. Cat. Invt. Foss., No. 18328. 



Microdiscus helena sp. nov. 



Head couvex, bordered all around by a continuous marginal rim that 

 is narrow at the back and sides and broad in front. Three small nodes 

 occur on the anterior lateral portion of the rim, the center one being on 

 the line of the frontal margin of the glabella. Glabella prominent, 

 cylindro conical, tumid posteriorly; two furrows cross the middle third 

 so as to separate a narrow central lobe, an anterior lobe nearly twice as 

 long as the central lobe, and a tumid posterior lobe that equals the an- 

 terior lobe in length. Dorsal furrows strong; the furrow within the 

 margin is broad and well defined all around except at the occipital fur- 

 row crossing the glabella, where it is very narrow ; it curves backward 

 inside the very narrow rim at this point. Cheeks tumid, and overhang- 

 ing the outer marginal groove. 



The pygidiae associated with the heads are strongly convex ; the me- 

 dian lobe, at the center, is a little more than one-third of the entire width 

 of the pygidium ; it is crossed by five transverse furrows that divide it 

 into five segments, and a short, terminal segment just inside the strongly 

 defined marginal groove ; dorsal furrows strong ; marginal rim narrow; 

 lateral lobes slightly convex, smooth. 



The head of this species is related to that of M. meeki and M. lobatus. 

 The tumid posterior lobe of the glabella serves to distinguish it from 

 them and also all described species. The associated pygidium differs 

 from that of M. bellamarginatus in being more convex and in having 

 five instead of nine segments in the median lobe. 



Formation and locality. — Lower Cambrian. In a decomposed 

 limestone, 600 meters west of Manuel's Broek, Conception Bay, New- 

 foundland. 



Nat. Mus. Cat. Invt. Foss., No. 183G1. 



Olenellus Hall. 

 See Bull. U. S. Geol. Survey, No. 30, 1886, p. 162. 



Thinking that Olenellus succeeded the genus Paradoxides in time, 

 and accepting the interpretation given by Mr. Ford to the embryonic 

 characters of 0. asaphoides, 1 argued iu favor of the descent of Ole- 



