Vol I. Grabau — Ordovician Fossils from North China (i) 51 



obliquely annulated outer wall are found in higher Ordovicir.n beds of this region. The 

 general similarity of the annulations to those of the siphuncle of Piloceras may indicate, 

 however, a similar camerated shell. 



Horizon and Locality: This species has been found in the Peilintze hmestone 

 associated with Archaiocyathus, Ojihileta squamosa etc., in the Shih-Mun-Chai- region near 

 Chingwangtao, Lingyiihsien district, Chihli province. Several specimens were collected 

 by Dr. F. F. Mathieu of the Kailan Mining Administration. The horizon is Lower 

 Ordovician. The specific name is given in honor of Mr. W. S. Nathan, president of the 

 Kailan Mining Administration, in appreciation of his keen interest in the development of 

 Chinese geology, and his recognition of the important place which stratigraphic and 

 palfeontologic problems hold in the practical development of mining interests. 



Chihlioceras chingw^angtaoense Grabau (sp. nov.) 



Plate II, Figs. 13a b. Text figures 14-16. 



Siphuncle longer and more cylindrical than in the preceding species, tapering at 

 the rate of 1 mm. in 6; section subcircular. Interior filled with crystalline calcium 

 carbonate, which has an indistinct radial structure. This occupies the space between the 

 shell or wall of the siphuncle on the one hand, and the wall of the compound endocone 

 (final endosheath) on the other. There are no indications of older sheaths, though these 

 may occur in the apical portion which is unknown. Endosiphuncle apparently central, 

 but the indications are faint. Wall of the endocone prolonged forward in a flat blade 

 which slopes forward, forming an angle of 12 degrees with the dorsal surface of the 

 siphuncle (See text fig. 14). If the rate of tapering is uniform, the length of the anterior 

 blade would approximate 110 mm, 



The blade is flat, except for a slight median longitudinal depression, most 

 marked in the alveolar portion. The lateral margins of the blade form a sharp angle with 

 the sides of the siphuncle, and the wall or shell of the latter was evidently continued over 

 at least the posterior part of the blade. Posteriorly the l)lade ends in the median 

 alveolus, the base of which occupies one third of the width of the siphuncle. Its height 

 is slightly less than the basal width, and its form is subtriangular but with curved sides. 

 Its position is approximately in the center of the siphuncle or slightly above it. Its depth 

 has not been ascertained, as some of the matrix which filled it, has not been removed. 

 The partition between it and the lateral alveoli is tliick, being from 7 to 8 mm. at the 



