PLATE XLVII. 



PAGE. 



Figs. 1 to 3 PlLOCBRAS NEWTON-WINCHELLI, sp. nOV 767 



1 and 2 Inner and profile views of the more complete specimen; showing the form of the 

 shell, the direction of the septa and, in fig. 1, the large size of the slpho. x 1 1-6. 



3 A fragment showing a portion of the filling of the sipho with traces of two siphonal 



sheaths. Shakopee chert, Union township, Houston county, Minn. 



Figs. 4 to 11 NANNO AULEMA, sp. nov 770 



4 Lateral view of a sipho with the aperture completed, indicating its freedom 



from the septal funnels 



5 Longitudinal section of a specimen broken at the top; showing the thickness of 



the preseptal cone, the convergent lines representing organic deposits. 



6 The most complete eiample observed; showing the form of the shell, the position 



of the sipho, three of the distal air-chambers and the relations of the preseptal 

 cone to the rest of the shell. 



7 to 9 Lateral and antisiphonal views of an average sipho, broken at the upper margin. 

 Figs. 49 from the Trenton shales, Minneapolis, Minn. 



10 Lateral view of a sipho bearing traces of annulations produced by the septa. 



From the Galena formation, Chatfleld, Minn. 



11 A portion of a sipho above the preseptal cone, showing very strong annulations 



produced by the septal funnels, and retaining a portion of the conch. Probably 

 from near Cannon Falls, Minn. 



Figs. 12 to 14 CYRTOCERINA (?) SCHOOLCRAFTI, sp. nov 774 



Lateral, septal and ventral (anti-siphonal) views of the original specimen. x3. 

 The sutures are shown on one side of the specimen, and in flg. 14. they have been 

 somewhat conventionally extended over the entire surface. Trenton shales 

 near Cannon Falls, Minn. 



Figs. 15 to 17 ACTINOCEEAS BIGSBYI Stokes 781 



15 View of the siphonal side of an internal cast of four air-chambers; showing the 



great size of the sipho and the filling of a portion of the endosiphon which is 

 somewhat displaced from its normal position. 



16 Outline of the distal septum of the same specimen. Trenton horizon, Minneapolis. 



17 Longitudinal section of a longer specimen, the upper part through the endo- 



siphon, and showing the thickness of the siphonal wall; the lower part through 

 the substance of the sipho. From the Trenton group near Rochester, Minn. 



Fig. 18 ACTINOCERAS BELOITENSE Whitfleld 782 



A portion of an internal cast showing the filling of the endosiphon. In the Tren- 

 ton limestone at Janesville, Wisconsin. 



Fig. 19 ORTIIOCERAS compare AMPLICAMERATUM Hall 790 



A fragment which retains traces of a fine longitudinal surface striation. 

 Galena limestone, Preston, Minn. 



Figs. 20 and 21 ORTHOCEUAS IULINEATUM Hall 786 



20 The apical part of a shell which shows very distinctly the gradual development 



of the annulations. x2. 



21 A fragment of a small shell with the characteristic exterior. This specimen is 



not very well preserved and the apparent absence of annulations on the upper 

 part of the shell is essentially due to imperfect retention. x2. Trenton 

 shales, Minneapolis. 



Figs. 22 and 23 ORTHOCERAS ANELLUS Conrad 784 



22 A portion of a small shell showing the characteristic annulation and surface 



ornamentation. 



23 Outline of the distal septum. Trenton shales, Minneapolis. 



