PLATE IV. 



Ordovician Cephalopoda; Lower Ordovician: Peilintze, Lianychiaslian, and Ycldi Lime- 

 stones; Upper Ordovician: Macltiakou Limestone. 



Drawings by K. C. Liu ($$ftij) 



Fig. 1. Protcrocameroccras niathieui Grabau p. 30 



la. Lateral view of a weathered specimen showing 'part of the siphuncle, and several 



camera, 1 . Natural size. 



Ib. End view of the same specimen showing aperture of endosiphocone. Natural size. 

 Ic. Section of the same showing form and position of siphuncle. Natural size. 



Peilintze limestone, Shih-Mun-Chai, near Chingwangtao, eastern Chihli. (Cotype, 



Coll. by F. F. Mathieu, G. S. Ch. Cat. No. 100) . 



Fig. 2. Prater oca mcroccr as mathicui Grabau p. 36 



2a. View of a small portion of the shell embedded in rock, showing flattened siphuncle 



and camera?, natural size. 

 2b. End view of the same, natural size; 

 2e. A portion of the shell and adjoining part of the siphuncle enlarged to show the 



relation of the siphuncular funnels to the outer shell on the ventral side, Peilintze 



limestone, Shih-Mun-Chai, near Chingwangtao, eastern Chihli. (Cotype, Coll. F. 



F. Mathieu, G. S. Ch. Cat. No. 101). 



Fig. 3. Proterocameroceras mathieui Grabau., p. 36 



3a. A free siphuncle in three sections. Natural size. 



3b.-3e. End views of the same at points indicated, x '2. Peilinlze limestone, Shih- 

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

 S. Ch. Cat. No. 102) . 



Fig. 4. Camcroceras styliforme Grabau p. 39 



4a. The siphuncle of a young or apical portion of a shell, showing the rate of tapering 



and oblique annulations. Enlarged twice. 



4b. Enlargement of the broken smaller end of the same specimen showing the flat 

 ventral side, the endosiphocoleon, and an older endosheath with open lumens 

 remaining; x 4. Liangchiashan limestone (Lower Ordovician), Liang-Chia-Shan, 

 Shih-Mun-Chai, eastern Chihli. (Cotype, F. F. Mathieu, G. S. Ch. Cat. 

 No. 103) 



Fig. o. Caineroceras styliforntc Grabau p. 39 



5a. Ventral view of an older portion of the siphuncle, showing the ventral saddle 



formed by the septa. Natural size. 



5b. Upper, and oc. lower ends of the fragment enlarged x 2. to show the endosiphoco- 

 leon. Liangchiashan limestone, Shih-Mun-Chai, near Chingwangtao eastern Chihli. 

 Lower Ordovician. (Cotype, Coll. F. F. Mathieu, G. S. Ch. Cat. No. 104). 



Fig. 6. Camcroceras xti/liforme Grabau p. 39 



6a. Lateral view of a silicified fragment of the siphuncle, of a more mature portion than 



that represented by figs. 4 & 5 showing portions of the septa adhering x 2. 

 6b. Upper and 6c. lower ends of the fragment, showing the last endosheath, its 

 continuation in the endosiphocoleon and indications of older sheaths x 2. Liang- 

 chiashan limestone, Liang-Chia-Shan Shih-Mun-Chai, near Chingwangtao, eastern 

 Chihli. (Cotype, Coll. F. F. Mathieu, G. S. Ch. Cat. No. 105). 



Fig. 7. Snecoceras yehliense Grabau p. 40 



7a. View of the type specimen as exposed on the rock surf-ace. Natural size. 



112 



