7b. Lateral view of tlie same, the left hand side is attached to the rock. Natural size. 

 Yehli limestone (Lower Ordovician), Yeh-Li, near Ma-Chia-kou, Chihli. (Holo- 

 type, Y. C. Sun Coll. G. S. Ch. Cat. No. 24). 



Fig. s. Suecoceras aitenuaium Grabau p. 41 



Apical portion of the siphuncle, showing rate of tapering. Natural size. Yehli 

 limestone, Yeh-Li, Chihli. (Cotype, Y. C. Sun Coll. G. S. Ch. Cat. No. 20). 



Fig. 9. Suecoceras attenuatum Grabau p. 41 



Silicified and partly broken specimen referred to this species, showing the last 

 endosiphosheath, and its excentric position. Natural size. Yehli limestone, Yeh- 

 Li, Chihli. (Cotype, Y. C. Sun Coll. G. S. Ch. Cat. No. 22). 



Fig. 10. Vaginoceras tsinancnsc Grabau p. 41 



10a, Ventral view of siphuncle, showing the strong saddle made by the septal necks. 

 Natural size. 



10b. Lateral view of the same, showing obliquity of septal necks. The left hand side is 

 attached to the rock. Machiakou limestone, Tangshan, Chihli. (Holotype G. S. 

 Ch. Cat. No. 25). 



Fig. 11. Piloceran platijveutruiit, Grabau : p. 42 



11a. Natural section of the siphuncle, showing the excentric endocone with flattened 

 venter; the endosiphuncle with its terminal projection (this is not as large as here 

 shown, some rock adhering which can not readily be separated) , and the crystalline 

 tilling. The specilnen is either a young form or the endocone extends further 

 apicad in this specimen than in others (see fig. 12). It is filled with rock matrix 

 enclosing foreign material, 

 lib. Side view of the same showing faint constriction at commencement of annulations. 

 Natural size. (The constriction is slightly over-emphasized owing to the position 

 of the specimen ) . 

 lie. End view of the same, showing position and form of endocone. Natural size. 

 Liangchiashan limestone, Shih-Mun-Chai region near Chingwangtao, eastern 

 Chihli. (Cotype, F. F. Mathieu, Coll., G. S. Ch. Cat. No. 108). 



Fig. 12. Piloceras platyvenirum Grabau p'. 42 



12a. Natural section of a siphuncle of a large and older specimen of subcircular cross- 

 section. The section is transverse to the dorso-ventral diameter but somewhat 

 oblique. The endocone with filling of rock-matrix, and the crystalline filling of the 

 earlier part with indications of older sheaths are shown. Natural, size. 

 12b. Side-view of the same, showing subcylindrical outline, with the oblique annulations, 

 which converge in a low broad saddle on the venter (right side) . The lower part 

 is fractured, showing complete filling with stereoplasm or organically deposited 

 lime. OMer sheaths are indicated in this fracture by dark lines. Natural size. 

 12c. End view (upper) of the fragment, showing the very slight flattening at this stage 

 of the endocone on the ventral side, which is the center of the convex surface (top 

 side of fig. 12c, right side of fiig 12b), as shown by the converging annulations. 

 The thickness of the lime-filled portion of the siphuncle is slightly greater on the 

 venter than on the sides. Liangchiashan limestone, of Liang-Chia-Shan Shih- 

 Mun-Chai region, near Chingwangtao, eastern Chihli. (Cotype, F. F. Mathieu, 

 Coll. G. S. Ch. Cat. No. 109). 



Fig. 13. Cliihlioceras nathani Grabau p, 48 



Ventral aspect of a typical specimen partly worn, but showing the endosiphuncle in 

 the lower part. (Sections of this specimen are shown in figs. 11 tt 12 of pi. II, 

 and a reconstruction in text-figures 2 to 6 pp. 45-40) Peilintze limestone near Ching- 

 wangtao, Chihli. (Cotype, F. F. Mathieu, Coll., G. S. Ch. Cat. No. 110). (See 

 also Plate V. which shows the upi^er side of the same slab on the under side of 

 which this specimen occurred) . 



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