Page:Walcott Cambrian Geology and Paleontology II.djvu/134

78 Formation and locality.—Lower Cambrian: (C17) ferruginous limestone nodules in the brown sandy shales at the top of the Man-t'o shale, at Ch'ang-hia, Shan-tung, China.

Collected by Eliot Blackwelder.

The cephalon of P. kochibei, in outline, wide fixed cheeks, broad frontal limb, and broadly rounded front margin of the gabella, is similar to the cephalon of Ptychoparia granosa Walcott (pl. 14, fig. 8). It differs in having a more pronounced swelling of the frontal limb in front of the glabella, more tumid fixed cheeks, and in surface characters. The surface of P. granosa is thickly studded with minute tubercles, while that of P. kochibei is smooth or possibly finely punctate; its frontal limb is also marked by fine, irregular, sometimes inosculating, rounded ridges that extend from in front of the glabella and palpebral ridges to the groove within the flattened frontal rim (pl. 14, fig. 10a).

The thorax has fourteen transverse segments with a narrow axial lobe and wide pleural lobes. The pleural furrow starts on the inner front side of the pleural lobe of each segment and, widening nearly to the width of the segment, begins to narrow at the point of geniculation and terminates near the posterior margin at the somewhat abrupt falcate termination of the pleura.

Pygidium small; the axial lobe is crossed by two furrows that serve to outline two transverse rings and a terminal section; two anchylosed segments are outlined on the pleural lobes on each side of the axial lobe by furrows that curve gently backward toward the faintly defined border.

Surface finely punctate or slightly roughened by minute depressions.

Observations.—This is the only Chinese species of Ptychoparia of which we have the entire dorsal shield; all the other species are represented by the separated parts. In outline the dorsal shield is not unlike that of Ptychoparia kingi (Meek), and it may be considered as the Chinese representative of that species.

The specific name is given in honor of the former Director of the Geological Survey of Japan, Doctor Kochibe.

Formation and locality.—Middle Cambrian: (35n, 35r, and 36e) Fu-chóu series; limestones and shales interbedded with limestones