320 BRANSON AND GREGER AMSDEN FORMATION OF WYOMING 



Tliis species is three to four times as abundant as any other in the 

 fauna. It is referred to C. trinuclea, though the larger forms might with 

 equal propriety be referred to 0. subquadrata. The means of the meas- 

 urements of a series of eight specimens are: Length, 18.5 millimeters; 

 breadth, 16.2 millimeters; thickness, 10.7 millimeters. 



There are many smaller specimens in tiie collection, but they are prob- 

 ably immature and show practically the same ratio of length, breadth, 

 and thickness as those measured. The largest specimen measured had a 

 length of 21 millimeters; breadth, 19 millimeters; thickness, 13 milli- 

 meters, and the smallest: Length, 16 millimeters; breadth, 14 milli- 

 meters; thickness, 9 millimeters. Some specimens show rather wide 

 variations from the type, one having a length of 22 millimeters ; breadth, 

 12.5 millimeters; thickness, 14 millimeters. Some forms show distinct 

 furrows on either side of the fold, while in others this feature is entirely 

 lacking. An arranged series would show all gradations from the deep 

 furrows to the absence of furrows. 



EUMETRIA YERNEUILANA (Hall) 

 Plate 18, figures 20-21 



1856. Retzia verneuiliana Hall, Transactions of Albany Institute, volume 4, 



page 9. 

 1914. Eumetria verneuiliana Weller, Illinois Geological Survey, monograph 1, 



pages 442-444, plate 76, figures 18-24. 



Only eight specimens of this species were collected. They agree with 

 Weller 's figures and descriptions excepting in the number of plications 

 being slightly smaller. Weller gives the usual number as 46 to 50, while 

 the eight specimens show brachial 36 to 42 and pedicle 36 to 40. 



CLEIOTHYRIDINA HIRSUTA (Hall) 



Plate 19, figure 14 



1856. Spirifera hirsuta Hall, Transactions of Albany Institute, volume 4, 



page 8. 

 1914. Cliothyridina hirsuta Weller, Illinois Geological Survey, monograph 1. 



pages 479-480, plate 80, figures 13-24. 



Two specimens from the Amsden are in the University of Missouri 

 collection. 



TETRACAMERA SUBCUNEATA (Hall) 



Plate 18, figure 18 



1856. Rhynchonclla suTjcuneata Hall, Transactions of Albany Institute, volume 



4, page 11. 

 1914. Tetracamera suhcuneata Weller, Illinois Geological Survey, monograph 1. 



pages 214-215, plate 28, figures 13-24. 



