NORTH AMERICAN GRAPTOLITES 65 
ing progressively more remote from one another. Thecz not well shown, 
about 25 in 25™". The main characteristic of this species is the remoteness. 
of the points of bifurcation and the small size of the branches. 
Horizon and locality.—Calciferous shales (zone with Dichograpsus flextlis, 
etc.), Point Levis, Canada. 
Dichograpsus abnormis (Hall). 
Herrmann’ regards this species as simply an ‘‘abnormal” specimen of 
D. rigidus. \ am unable to agree with this view, the species apparently 
being well characterized. 
TETRAGRAPSUS SALTER, 1863. 
Quart. Jour. Geol. Soc. London, XIX., p. 140. Type 7. cruczadzs Salter.. 
Tetragrapsus acanthonotus Gurley, sp.nov. Plate IV., Figs. 1, Ia. 
Width of branches from apex of thece to virgula, 2.5—3™™. Dorsal mar- 
gins at intervals of from I to 3 thece (generally opposite every other theca): 
bearing spines 1™™ or less in length, which are integumentary processes, not 
connected with the virgula. Thece 17 to 20 in 25™™, slightly curved with. 
the upper lip produced into a rather acute denticle. Line of aperture con- 
cave, inclined (on distal side) to virgula about 120°. 
Horizon and locality.—Calciferous shales about one and one-quarter miles: 
N.N.W. of the East Railway Station, at Point Levis, Canada, opposite the 
iron foundry. ' 
Recognizable at a glance by its spinose dorsal margin. The generic ref- 
erence is made from a single small specimen seen. 
DiIDYMOGRAPSUS McCoy, 1851. 
. Brit. Palaeozoic Fossils, p. 9. 
Didymograpsus bipunctatus Gurley, sp. nov. Plate V., Figs. 7, 7a. 
Sicula slender, short. Branches diverging from sicula at an angle of 110°, 
very slender, with an undulating dorsal margin, each undulation correspond- 
ing toa theca. Thecze about 65 in 25™™", curved, equally wide throughout, 
with the apertural margin straight, and retrotruncate. Between each pair of 
thecze are two “pustules” (one at base of proximal theca, the other near its 
distal end), appearing as though joined by an elevated line. Owing to the 
close proximity of the series of elevated lines, the specimens, viewed in some 
directions, appear to possess a continuous undulating raised line. 
Horizon and locality.-—On a slab of Calciferous shale in a small collection 
from one mile N.W. of the East Railway Station, Point: Levis, Canada. A 
dozen specimens, mostly small or immature, were seen. 
«Nyt Mag. f. Naturvid, 1885, XXIX., p. 210. 
