CRUSTACEA. 
71 
They may, however, be distinguished by the strong occipital spine, the stouter 
marginal spines, and the more depressed and broader glabella in the latter 
species. 
Distribution. Upper Helderberg group. Schoharie grit; Near Clarksville, 
Albany county; Corniferous limestone; Camillus, Onondaga county; in the 
decomposed chert boulders, Canandaigua, Ontario county; Cayuga, Province 
of Ontario. 
Acidaspis, sp. 
PLATE XVI B, FIG. 14. 
A SINGLE large pygidium from the decomposed chert at Port Colborne, 
Ontario, is shorter than in the foregoing species, the axis more arched, with 
a very strong articulating ring and a single annulation which becomes obsolete 
on the flat pleurae, but the bases of two stout marginal spines represent its 
termination on the postero-lateral border. The rest of the margin appears to 
be fringed with small, irregularly disposed spines and spinose tubercles. The 
termination of the axis is less abrupt than in A. callicera and without the char¬ 
acteristic tubercles of that species. The specimen has a length of 9 mm., and 
a width of 21 mm. 
Acidaspis Romingeri, n. sp. 
PLATE XVI B, FIGS. 15-18. 
Pygidium comparatively large; surflice very convex; anterior margin transverse. 
Axis conspicuous, short, unsegmented, bullate ; outline circular; articulat¬ 
ing ring broken away, the transverse furrow behind this ring being shallow 
and narrow. The posterior portion of the axis is sub-spherical, slightly 
constricted about the base and flanked on the antero-lateral margins by two 
elongate nodes. The longitudinal furrows are conspicuous, being abruptly 
depressed near their anterior terminations. Border broad, depressed about 
the axis, flattened toward the margin, bearing twelve long spines. Of these, 
ten are marginal, the third spine on either side being very much longer than 
the others and attaining a length equal to more than five times the length of 
