GRAPTOLITES. 91 
Puate VI. 
1. A fragment showing two of the stipes entire, and the bases of two others ; the 
radicle extending to the margin of the specimen. 
2. A specimen preserving three of the stipes, one of them entire, and showing some 
irregularities in the bifurcation where the one is broken off. 
3. Anenlargement of the right-hand stipe of the specimen fig. 1. 
Formation and Localities.—Shales of the Quebec group; at the upper 
end of Orleans Island, and three miles above river St. Anne. 
15. GRAPTOLITHUS QUADRIBRACHIATUS, Hall. 
Plate V, figures 1-5; and Plate VI, figures 5, 6. 
(G. quapripracHtatus, Hall: Geological Survey of Canada, Report for 1857, page 125.) 
Description.—Frond composed of four simple undivided stipes arranged 
bilaterally, or two proceeding from each extremity of the funicle. Stipes 
slender, very gradually increasing in width from their origin, as far as traced ; 
usually straight, sometimes slightly curved ; width from two to four hun- 
dredths of an inch at the base, and im the most perfect examples, nine 
hundredths of an inch at the widest part. The back of the stipe is marked 
by a filiform axis, and there is scarcely more space occupied by the common 
body. ‘Test thin, though well preserved in the finer shales. Surface of 
cell-walls distinctly striated parallel to the apertures, and the cell-partitions 
visible nearly to the back of the stipe. 
Cellules narrow, scarcely curving, and slightly expanding towards the 
aperture, making an angle with the axis of about 38°; the length equal 
to about four diameters, the free portion being from one third to two 
fifths their entire length. The margin of the aperture is nearly straight, 
or very slightly curved, making an angle of from 95° to 100° with the 
axis. The number of cellules in the space of an inch is from twenty-two to 
twenty-four, dependent on the distance from the origin of the stipe, and on the 
degree of development. The apex of the denticle, or posterior point of the 
aperture, is a little below the base of the second cellule in advance. Cell- 
partitions thin, and usually not well preserved. 
This species, when entire, is readily distinguished from G*. bryonotdes 
by its straight and more slender branches, and by the general aspect and 
expression of the fossil; it has only a remote similarity with the other 
quadribrachiate forms. In separated or double stipes it bears some 
