Explanation of Plate XIII. 



¥iG . 1 . Amplexus blairi 108 



Longitudinal section. (Mus. Mo. Geol. 8ur ) 

 Carboniferous, Burlington limestone. 



JFiG. 2. Amplexus yandelli^ 108 



Lateral view of a well-preserved specimen. (Mus. Mo. Geol. Sur.) 

 Carboniferous, Kinderliook limestone. 



Fig . 3. Columnaria stellata 116 



A medium-sized mass. (Mus. Mo. Geol. Sur.) 

 Silurian, Trenton limestone. 



Fig. 4. Zaphrentis acuta 109 



Lateral view. (Mus. Mo. GeoL Sur.) 

 Carboniferous, Kinrterhoolc (Louisiana) limestone. 



Fig. 5. Zaphrentis cylindracea Ill 



Longitudinal section. (Mus. Mo. Geol. Sur ) 

 Carboniferous, Kaskastia limestone. 



Fig. 6. Zaphrentis elliptica HI 



6a. Side view of a well-preserved specimen. (Keyes collection . ) 

 6b. View of same from above. 



Carboniferous, Burlington limestone. 



Fig. 7. Campophytlum torquium 107 



An unusually large and twisted specimen. (Hare collaction.) 

 Carboniferous, Upper Coal Measures. 



Fig. 8. Lophophyllum proUferum ._ 115 



8a. A large example (Hare collection). 

 8b . A smaller individual . (After Meek ) 

 Carboniferous, Upper Coal Measures. 



Fig . 9. Streptelasma corniculum 117 



Lateral aspect. (Mus. Mo. Geol. Sur.) 

 Siinrian, Trenton limestone. 



Fig. 10. Zaphrentis tenella HI 



An average-sized example. (Mus. Mo Geol. Sur.) 

 Carboniferous, Keokuk limestone. 



Fig. 11. HadrophyUum glans lie 



11a. Side aspect. (Keyes collection ) 

 lib. View of same from above. 



Carboniferous, Burlington limestone. 



Fig. 12. zhphrentis dalei 113 



A large example . (Mus. Mo. Geol. Sur.) 

 CarboniferoQs, Keokuk limestone. 



