(ii) S8 Palaeontologia Sinica Ser. B. 



Genus ENOOCERAS Hall 



Endoceras leei Yu (sp. nov.) 



Plate I., Figs. 6, ya-b. 



Ectoconch straight, cylindrical. Form of cross section unknown. Endoconch 

 elliptical, of considerable size and filled with conical endosepta. Ectosepta crowded. 

 Tapering of ectoconch very gentle. Endotheca absent. 



This specimen is represented only by a portion of the ectoconch exposed on the 

 surface of a polished slab. Its actual length is unknown. The width at the lower 

 end of the preserved fragmentary part is 30.5 mm. At a point about 81 mm. from the 

 lower end it has a breadth of 36.5 mm. This gives the rate of tapering about i mm. in 

 a length of 13.5 mm. 



The ectosepta are very numerous and strongly concave, with a concavity about 

 one and a half times their distance apart at the center. The interspaces between them 

 are nearly equal, averaging about 6.5 mm. apart. The ectosepta are provided with 

 long tubi, which distinctly show that they extend from the ectoseptum where they 

 originate to a distance of one camera toward the apex. 



The endoconch is situated excentrically. Its size is remarkably large, having 

 a maximum width of 2/3 that of the ectoconch or more. The interior of the endoconch 

 is occupied by endosepta tapering off at the center into a narrow endosiphuncle. From 

 the cross section at the lower preserved end we find that the endosiphuncle is oval in 

 outline, measuring 0.7 mm. and 0.9 mm. in the shorter and the longer diameter respec- 

 tively. At the same stage the corresponding longer diameter of the endoconch is 14 mm. 

 The endoconch bounded by the last endoseptum has a subtriangular section with an 

 apical angle of 20°. 



Both the camerre of the ectoconch and the endoconch are filled with the red lime 

 matrix, in which the shell of this specimen is embedded. Many of the ectosepta, 

 however, show a slight stereoplasmic thickening on their upper, and more rarely on 

 their under side as well. 



There is another specimen (Plate I., Fig. 7.) probably of the same species. The 

 endoconch attains a length of nearly 160 mm. The space below the final endoseptum 

 of the endoconch has been wholly converted into the crystalline deposit, but the 

 terminal endocone is empty. The ectoconch is partly crushed, preserving however 

 ectosepta around the upper part of the endoconch. At the lower extremity a very 



