DESCRIPTION OF GENERA AND SPECIES. 123 



the character of the glabella and the form of the associated pygidium; the straight, 

 flat furrow on the pleural lobes of the thoracic segments is of the same type as 

 that of Olenoides and Dorypyge [plate 8]. 



The species differs from Blackwelderia cilix [plate 9, figs. 6, 6a-b] in the character 

 of the frontal limb, its broader fixed cheeks, and in the form and character of the 

 spinose border of the pygidium. 



M. Bergeron described his Calymmene ? sinensis from a few specimens of the 

 central portions of the cephalon, and his Olenoides leblanci from specimens of a 

 pygidium associated with the cephala. The much better material now available 

 for study indicates that the cephala and pygidia belong to the same species, and I 

 therefore unite them under the term B. sinensis, as that name occurs first in order 

 in M. Bergeron's paper. 



For comparisons between this species and B. cilix see observations under that 

 species [p. 119]. 



Formation and Locality. Middle Cambrian: (('(>) Thin, platy limestone in 

 the upper shale member of the Kiu-lung group [Blackwelder, 19070, pp. 37 and 41 

 (second list of fossils), and fig. 10 (bed 12), p. 38], 2.5 miles (4 km.) southwest of Yen- 

 chuang, Sin-t'ai district, Shan-tung, China. 



Collected by Eliot Blackwelder. 



Also from Locality 36f, Middle Cambrian: Fu-chou series; about 1,000 feet 

 (305 m.) above the white quartizte [see Blackwelder, 19076, p. 92, for general strati- 

 graphic relations], 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. 



Genus DAMESELLA Walcott. 



Damesella WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 34. (Genus described and discussed.) 



General form elongate, ovate, distinctly trilobate, moderately convex. Ceph- 

 alon transversely semicircular, with the postero-lateral angles rounded or spinif- 

 erous; the anterior and lateral margins have a thickened or elevated border, within 

 which there is a well-marked furrow. Glabella truncato-conical, marked by two 

 or more pairs of short furrows; occipital furrow strongly defined; occipital ring 

 rounded. Fixed cheeks rather broad. Free cheeks subtriangular in outline, rising 

 with a gentle curvature to the base of the eye-lobe; the border is extended into a 

 lateral spine a short distance in advance of where it is cut by the facial suture. 

 The facial suture, cutting the anterior border nearly opposite the base of the inner 

 margin of the palpebral lobe, extends with slight curvature backward to the pal- 

 pebral lobe; curving about the latter, it extends outward and backward, cutting 

 the posterior margin a little in front of the rounded postero-lateral angle. Eyes 

 small, elevated, and situated about midway of the glabella. 



Hypostoma subrhomboidal in outline ; central portion strongly convex, elevated, 

 with an irregular border at the back and sides, broadening out in front to a greater 

 width than at the back. 



Thorax with twelve or more transverse segments; axis about one-third the 

 width of the thorax, gradually narrowing posteriorly. Pleurae nearly horizontal, at 

 right angles to the axis out to the point where they curve gently backward before 

 terminating in a falcate extremity; pleural groove long, deep, and broad, starting at 

 the dorsal furrow near the front and extending out on the falcate end. 



Pygidium subsemicircular ; axis convex, broadly conical, and divided into four 

 or more rings by transverse furrows; lateral lobes depressed, convex, and divided 



