Vol. I C. C. Yu--Ordovician Cephalopoda of Central China (ii) S9- 



small section of the endosiphuncle may be seen in the central part of the endoconch, 

 being about 0.3 mm. in diameter and filled up with the red lime matrix. In the same 

 place the endoconch is sub-elliptical in section, measuring 9 mm. in its major diameter, 

 and 7 mm. in minor. The apical angle of the final endoseptum is nearly the same as 

 that in the preceding specimen. The cameras of the ectoconch are entirely free from 

 any deposit except the ectosepta, which are also slightly thickened as in the preceding 

 specimen. 



Comparison: This species bears a close resemblance to Endoceras (Cyclendoceras) 

 annulatum Hall' from the Trenton limestone at Watertown New York. But Hall's 

 form has the ectosepta more approximate as compared with the diameter of its 

 ectoconch. Moreover, the annulated ectotheca is not recognized with certainty in the 

 present species, though there seems to be an indication of it in the undulating profile 

 along the sides of the ectoconch in the polished longitudinal section. 



Horizon and Localities: One specimen (Plate I., Fig. 6.) was collected from 

 the red thin-bedded limestone of the upper division of Middle Ordovician age at 

 San-shan-yuan ( S llj M ) and the other (Plate I., Fig. 7.) from the same horizon at 

 He-chiao {^ 1^), Chung-yang-hsien. The specific name is given in honor of Professor 

 J. S. Lee. (Coll. C. Li and W. P. Shu) 



Endocsras grabaui Yu (sp. nov. 

 Plate II., Fig. 4. 



General form cylindrico-conical, more or less elongate, slightly arcuate, gradually 

 diminishing toward the apex, and elliptical in cross section; endoconch very broad, 

 enclosed by the continuous tubi, not forming a straight tube but giving the sides of 

 the endoconch the appearance of an irregular undulation. 



The ectoseptal intervals are slightly variable in their distance apart from one 

 another, ranging from 9 to 11 mm. throughout the whole length of the fragment. The 

 ectosepta are thin and very deeply concave, having a convexity of more than one septal 

 distance. The ectoseptal tubi are continuous, but extend across the different ectoseptal 

 spaces in different ways. Thus some of them are bent inwards; some nearly straight 

 and slightly oblique toward the interior; and finally some tubi turn inwards at first and 

 gradually backward as well as outwards. 



I. J. Hall: Palaeontology of New York, Vol. I, p. 207, pi. XLIV, figs, i a,b. 



