104 WINCHELL AND MARCY ON FOSSILS FROM THE 



The pygidiuiin is also imperfectly known. It consists of at least three joints. The axis 

 is moderately elevated anteriorly; the first two segments are narrow, the third much wider, 

 and its depressed and narrowed posterior portion extends apparently to the caudal extrem- 

 ity. The flattened and expanded pleurae are surmounted each by a pair of broad, elongated, 

 obtusely terminated, pad-like elevations, which terminate much short of the tips of the 

 pleurae. In two large specimens these elevations are separated from each other, and from 

 contiguous pairs, by an intervening flat area. The basis of the granular crust is marked, 

 as in the thorax, by concentric imbricating wrinkles. Characters of the margin unknown. 



Length of cephalic shield to the collar, 1.8 inch ; greatest width of anterior region of 

 middle lobe, 1.0 inch; length of lateral lobe, 1.0; width of lateral lobe of thorax, more than 

 two inches ; length of pygidium, more than three inches. These parts may belong to 

 different individuals. 



We at first imagined the conspicuous and unique fragments of this .large species to belong 

 to L. Nereus Hall, which, in a general way, it strongly resembles. It may be distinguished 

 by the absence of a "proboscis," and the want of articulations in the peripheral area of the 

 caudal shield. A pygidium, with a similar flat inarticulated flap, is seen in Lichas canadensis 

 Logan, (Can. Eep. 1844, p. 54). 



Lichas decipiens W. and M. 

 Plate III. figure 11. 



Pygidium semi-elliptic, of three articulations, with a prominent axis and a flat border. 

 Two anterior joints of axis, narrow ; posterior consisting of an anterior narrower portion 

 and a posterior depressed portion, rapidly subsiding to a level with the lateral lobes, and 

 tapering to a point before attaining the caudal extremity. The ribs are broad, flattened, 

 expanding, divided by a median groove, and terminating in short free points. The anterior 

 rib is nearly transverse at its origin, and distinctly curves backward. The second makes an 

 angle of 45 with the axis and is less curved. The third is straight, and its posterior lobe 

 or moiety is parallel with the axis, meeting the corresponding moiety of the posterior rib 

 of the opposite side. The surface is densely granulated. 



Length of pygidium, .5 inch ; width, .6 inch. 



BRONTEUS Goldfuss. 



Bronteus occasus W. and M. 



Plate III. figure 12. 



Pygidium with the axis consisting of two articulations. The limb slopes laterally and 

 posteriorly, and is marked by seven equal ridges radiating on each side from the axis, and 

 one additional on the median line, all becoming confluent around the border. These 

 ridges, or rays, exhibit but very little curvature. The median (or posterior) ridge is nearly 

 twice as broad as the others ; the extreme ridges on the right and left are at right angles 

 with the axis. The general outline is parabolic. Neither striae nor granulations are ap- 

 parent. 



Length, .48 inch ; breadth, .62 ; length of axis, .13 ; breadth of axis, .23 inch. 



Several small pygidia in our collection, very well preserved, appear to be distinct from 

 any described species known to us. They differ from B. flabellifer Goldf. which has been 



