Page:Walcott Cambrian Geology and Paleontology II.djvu/135

NO. 4 near the base of the series just above the white quartzite, collected in a low bluff on the shore of Tschang-hsing-tau island, east of Niang-niang-kung, Liau-tung, Manchuria, China.

Collected by J. P. Iddings and Li San.

This subgenus differs from Ptychoparia in its smooth glabella and larger palpebral lobe; from Liostracus, in having an arched or nearly flat frontal limb and rim and more convex cranidium; from Conocephalina, in its smoother glabella and wider fixed cheeks; and from Anomocare, in its smoother glabella, usual absence of distinct palpebral ridge, proportionately shorter eye lobes, and glabella.

Genotype.—Ptychoparia theano Walcott. (pl. 14, figs. 9, 9a.)

Observations.—This subgenus is characterized by a nearly smooth surface on the glabella and fixed cheeks, rather large palpebral lobes, and narrow postero-lateral limbs. Unfortunately, no entire specimens of the cephalon and thorax are known, and the pygidia referred to it may or may not belong to the species to which they are tentatively assigned. Only when a thorough study is made of all the material within the Conocephalinæ will it be possible to make even a fairly adequate grouping of the species.

Of the species of this subgenus from China, P. (E.) theano (Walcott), P. (E.) bromus (Walcott), and P. (E.) eriopia (Walcott) have the posterior, elongate palpebral lobe. In P. (E.) mantoensis (Walcott) and P. (E.) constricta (Walcott) the palpebral lobe is much like that of Ptychoparia in its position.

Stratigraphic range.—Ptychoparia (Emmrichella) mantoensis and P. (E.) constricta occur at the summit of the Lower Cambrian; P. (E.) eriopia and P. (E.) theano, at the base of the Ch'ang-hia formation of the Middle Cambrian; and P. (E.) bromus, at about the same horizon in the Kiu-lung formation.

The cranidium of this species differs from that of C. damia (Walcott) in its shorter frontal lobe, flatter frontal rim, and proportionately longer glabella. The associated pygidium has a proportionately shorter axial lobe and its sides curve outward instead of inward.

Formation and locality.—Middle Cambrian: (35r) Fu-chóu series; limestones near the base of the series just above the white quartzite,