(i) 82 Palseontologia Sinica Ser. B 



figure 6 on Plate VII, the same camera may show a thickening on one side to the 

 extent of half the height of the camera, while on the opposite side the thickening may 

 fill nearly the whole of the camera. In a general way, there is a decrease in the amount 

 of the deposit from the older septa forward to the younger. 



The apical end of this species is shown in a specimen from Tangshan (Plate VII, 

 figs. 7a,b). This begins with a somewhat asymmetrical subconical initial chamber, about 

 9 mm. in depth. At its apex is the large siphuncular foramen, surrounded by a swollen 

 annulus, the whole producing an apical mammelon, about 7 mm. in basal diameter. The 

 central scar or siphuncular opening is about 3.5 mm. in diameter. At its upper end the 

 initial chamber has a lateral diameter of 16.6 mm. and a dorso-ventran of 16 mm. The 

 mammelon lies to one side of the lateral, but, on the dorso-ventral axis. Above the 

 initial chamber the ventral (?) side (side nearest to which the siphuncle lies) becomes 

 faintly concave longitudinally as if the shell were taking on a cyrtoceraconic form. This 

 continues for about five chambers after which it disappears and the surface slope is 

 normally orthoceraconic. Almost from the first the septa average 3 mm. apart at the 

 suture, their concavity being equal to about the depth of one camera. This early portion 

 of the shell has a somewhat greater angle of divergence than is characteristic of later 

 stages, being about 1 in 4. 



Surface features of shell unknown. 



This form is readly distinguished by its slender character, gentle rate of tapering, 

 septal distance, character of stereoplasm and excentric siphuncle. The latter is not 

 however always seen in its true relation in longitudinal section, for if this is normal to 

 the dorso-ventral axis the siphuncle appears centran as in fig. 6 Plate VII. 



HORIZON AND LOCALITY: A. tani is probably as common as, if not more so than 

 A. richthofeni, and occurs in practically the same localities, in the Machiakou limestone. 

 Specimens have been obtained from Tangshan (F. K._ Morris, G. B. Barbour), Machia- 

 kou (H. C. T'an), and Chaokouchuang (Survey expedition) Chihli; from Lincheng, 

 from Chan-chin-Hsien, and elsewhere in Shantung (F. F. Mathieu, J. G. Andersson and 

 V. K. Ting) and from Chilio, south of Shih-T'ou Chiang, Chihli (G. B. Barbour). 

 The specific name is given in honor of Mr. H. C. T'an of the Chinese Geological 

 Survey. 



Actinoceras coulingi Grabau (sp. nov.) 

 Plate VIII, figs. 1, 2. 



1903 Actinoceras (Ormoceras) aff. tenuifilum Hall. Crick, Geological Magazine N. Ser. Dec. 

 IV, Vol. X, p. 481, pi. XXII fig. C. 



