CRUSTACEA. 71 



They niay, 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 gril : Near Clarksville, 

 Albany county; Corniferous limestone: Caniillus, 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 pleura?, 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 nun., and 

 a width of 21 mm. 



ACIDASPIS KOMINGERI, 11. Sp. 

 PLATE \\ I B, PIGS. 15-18. 



Pygidium comparatively large; surface 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 Hanked on the anterolateral 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 



