(i) 52 



PalfEontologia Sinica 



Ser. B 



rounded forward end, and increasing in thickness apicad. (See section, text figures 15 and 

 16). It consists of the thin endoconic walls (reduplications of the endosheath) and the 

 filling of crystalline calcium carbonate between these. 



Fig. 14. Chihlioceras chingwangtaocwe. Diagrammatic longitudinal section along the median dorso-ventral 

 plane of a restored individual; m-n. -section line of fig. 15; o-p. -section line of fig. 16; h. -shell (ectosiphuncular wall;; st. 

 stereoplasmic filling; s/.-endosiphotube; en. -endoconic lining or terminal endosheath; (fa. -dorsal alveolus; ma. -median 

 alveolus. 



The lateral alveoli are lenticular in section, only the inner, gently concave wall 

 being formed by a part of the endosheath, while the outer is formed by the wall of the 

 siphuncle, and in the type specimen, as preserved, is broken away. In this specimen the 



size and form of the two lateral" alveoli differ from each other, 

 that on the right * being much larger. The line of junction 

 between it and the siphuncular wall (shell) is a direct con- 

 tinuation of the plane of the anterior endoconic blade. The 

 sides of this alveolus converge regularly. The left lateral 

 alveolus is more irregular. At first there is a strong conver- 

 gence of the sides, after which they continue more nearly 

 Fig. 15. chihiioceras ching- Uel p oster iorly the two alveoli join into a single broad 



wfingtaoense. Diagrammatic cross- 

 section along line m-n. in fig. 14; median cavity, the floor of which is formed by the two lateral 



q-r. -median dorso-ventral plane 



(line of section of fig. 14); -.-iine alveolar floors meeting m a low angle, to the left of the 

 of section of fig. 16; *a.-iaterai median line in tne type specimen. (See fig. 13a Plate II). 



.alveoli; other notations as in fig. 



14. The length of this posterior confluent cavity can be estimated 



from the slopes of the lateral alveoli, this being indicated in the restored longitudinal 

 section (text figure 14). 



The inner shell or siphuncular wall, is about 0.3 mm. in thickness and strongly 

 and regularly annulated upon the sides, these annulations forming an angle of approxi- 

 mately 82 with the dorsal surface, or 70 with the plane of the anterior endoconic blade. 



* The shell is oriented with the apex to the observer, the aperture or anterior end pointing away, and 

 the ventral side, (i.e. flattened side of endocone), downwards. The right and left sides then correspond to the observer's 

 right and left hand. In the figures on Plate II the position is reversed, so as to show the structure more clearly; therefore 

 the references must also be reversed from those here given. 



