80 PALEONTOLOGY OF NEW YORK. 



Petersb., 7th Ser., vol. xxxiii, No. 1, p. 42. 1885), to the sub-genus Cono- 

 lickas, Dames, of which L. triconica, Dames, and L. Schmidti, Dames, are the 

 types In ;ill the species enumerated by these authors, the third pair of lateral 

 lobes is present in varying degrees of development. In L. Eriopis, however, 

 il appears to lie obsolete or represented only by a pair of tubercles; but as the 

 general form of the head is the feature upon which the sub-genus is based, the 

 obsolescence of these lobes will not vitiate the reference of the species to this 

 group. 



Distribution. Upper Helderberg group. Corniferous limestone : Schoharie, 

 Schoharie county ; in the boulders of decomposed chert, Canandaigua, Ontario 

 county. 



In order to correct, and to a certain degree, to complete the original determi- 

 nations of the species of Lichas occurring in the Lower Helderberg formations, 

 a few observations are here introduced. 



Lichas (Conolichas) pustulosus. 



PLATE XIX, FIGS. 8, 10, 11. 



Lichas pustulosus, Hall. Pal. N. Y., vol. iii, p. 366, pi. Ixxvii, figs. 0. 10: pi. lxxviii, figs. 1-8. 1850. 



Lichas (Conolichas) Bigsbyi.? 



PLATE XIX A, FIG. 1. 

 Lichas Bigsbyi, Hall. Pal. N. Y., vol. iii. p. 364, pi. Ixxvii. lig-s. 1-7 (S ?) ; pi. lxxviii, tigs 5, 6(»). 1S5S1. 



Lichas (Conolichas ?), sp. ? 



PLATE XIX, FIG. 9. 

 Lichas pustulosus, Hall. Pal. N./V"., vol. iii. pi. lxxviii., tig. 7. 1859. 



Recent careful investigations of the trilobitic layers of the shaly limestone in 

 the vicinity of Clarksville, Albany county, have shown that the cephala of Lichas 

 pustulosus are found in close association with pygidia quite distinct from those 

 originally ascribed to that species. These bear broad, sub-lanceolate, recurved 

 spines on tin- lateral margins in two pairs only; the posterior extremity 

 terminating in a single broadly rounded lobe. This form of pygidium, and 



