NATURAL SCIENCES OF PHILADELPHIA. 23 



sions shallow, quadrangular, or transversely rhombic (those on the upper pari 

 being quadrangular, and those farther down becoming mure rhombic, and 

 wider than high), arranged in spirally ascending rows, which make nearly 

 one turn in passing from the base to the centre of the top; each with a trans- 

 verse linear central furrow, from which a similar furrow passes to the lower 

 angle ; central perforations of the cell depressions minute, and generally closed 

 in the typical specimen. 



Height, 1-75 inches; breadth, 1-22 inches. 



This species differs from all others known to us, especially from any Upper 

 Silurian horizon, in its elongated, obovate form, its outline being almost ex- 

 actly obovate, excepting the truncation of the lower (smaller) end. In gem 

 appearance it perhaps most nearly agrees with a form found in the Galena 

 Limestone, and referred by us, doubtfully, to R. globular is, Hall, in the third 

 vol. Illinois Geol. Reports, pi. 2, fig. 2 a,b. It differs, however, from that 

 species in having the upper end more round, or less depressed, and without 

 any umbilicoid impression. Its cell impressions are also very different, not 

 being near so crowded, and instead of becoming more crowded and narrower 

 on the lower half, they are less so there than above ; while the central per- 

 foration of each is much smaller. 



Locality and position. Bridge Port, near Chicago, Illinois. Niagara Group 

 of Upper Silurian. 



We are under obligations to the Rev. E. C. Bolls, of Portland, Me., for the 

 use of the only specimen of this species we have seen. 



ECHINODERMATA. 



Barycrinos spectabilis, M. and W. 

 Body attaining a large size, rather deeply cup-shaped, though wider than 

 high ; truncated below, with sides moderately expanding upward. Base 

 basin-shaped. Basal pieces rather large, nearly twice as wide as high, penta- 

 gonal in form, with the mesial angle above deeply impressed, the impression 

 being also continued down the middle to the lower edge, with a broad promi. 

 nence or ridge on each side of it also extending to the lower edge, where 

 each of these prominences terminates in a little angular projection, while the 

 lateral margins are strongly and abruptly beveled, so as to form deep, wide 

 notches at the sutures. Subradial pieces large, hexagonal, excepting one on 

 the anal side, which is heptagonal ; all very profoundly impressed at the cor- 

 ners, so as to form strong, radiating ridges, extending one to each of the sides. 

 to connect with those on the other contiguous plates; sometimes these ridges 

 terminate in pinched-up nodes on the central region. First radial pieces 

 about twice as wide as high, being generally a little wider than the BUDradials, 

 pentagonal in form, with superior lateral angles more or less truncated, and 

 slightly projecting at the edge, each with its broad, very shallow sinus above, 

 forthe reception of the second radials. more than three-fourths as wide as its 

 upper margin, while the deep impression at the lower angles form two broad, 

 very strong ridges, extending downward to connect with those on the sub- 

 radial s ; sometimes these terminate near the middle above, in sharp pinched- 

 up, diverging nodes, or short carinas, while between these and the superior 

 lateral, truncated angles, one or two other sharp prominences are somel 

 seen. Second radial pieces extremelv short, or almost transversely linear, 

 and not always entirely filling the broad shallow sinuses in which they rest. 

 Third radials triangular, a little higher in the middle than the first, out 

 wedo-in^ to a very thin edge on each side, or even sometimes thinning out so as 

 to let the first brachial pieces rest, at the lateral ends partly upon the first and 

 partly on the second radials. Anal pieces of moderate size, quadrangular in 

 form, a little wider than high, and resting on the upper truncated edge 0< the 

 heptagonal subradial, while its own upper edge is truncated entirely aci 

 nearly on a level with the superior lateral angles of the first radial on 

 side of it. 



1870.] 



