34 Annals of the Carnegie Museum. 



Spirifer whitneyi Hall. Lime Creek, Iowa. 



Ratio (i), range I : .6 to i : .77. Ratio (2), range i : .23 to i : .24. 

 Ratio (3), range i : .86 to i : i. 



Spirifer whitneyi Hall. Three Forks, Montana. 



Ratio (i), range i :.47 to i : .69. Ratio (2), range i : .17 to 

 I : .27. Ratio (3), range i : .5 to i : .8. An average specimen from 

 Three Forks has a width of 32 mm. a height of 21 mm., height of area 

 of 7 mm., and width of delthyrium of 5.7 mm. 



The number of plications on each side of the brachial valve and the 

 number on the fold is as follows: 



Sptrifer disjnndus from Boulonnais, 18 to 31 on a side, majority 21; 

 9 to 13 bifurcating plications on the fold, majority of specimens have 

 II. 



Spirifer whitneyi from Lime Creek, 16 to 26 on a side, and 7 to 12 

 on the fold. 



Spirifer whitneyi from Three Forks, 16 to 26 on a side; majority 21 ; 

 and 8 to 15 on the fold. 



5. Spirifer whitneyi var. animasensis (Girty). (Plate V, figs. 11-13.) 



Spirifer disjunctus var. animasensis Girty, Twentieth Ann. Rept. U. S. G. S., pt. 2, 



1900, p. 48, PI. 4, figs. i-io. 

 Spirifer whitneyi var. ani7nasensis (Kindle), U. S. G. S. Bull. 391, p. 25, PI. 9, figs. 



1-3- 



About twenty of the spirifers from the Three Forks Formation have 

 been identified by the writer as Spirifer whitneyi var. animasensis 

 (Girty). These specimens are somewhat smaller than Spirifer 

 whitneyi and they all show a relatively high area with frequently a 

 slightly twisted ventral beak, and they compare well with the specimens 

 figured by Drs. Girty and Kindle. The ratio of the width to the height 

 of the brachial valve in the Montana specimens range from i : .5 

 to I : .76 and the ratios of width to height of area from I : .28 to 

 I : .33. The ratios of the height to the width of the delthyrium 

 range from i : .46 to i : i. The ratios of the specimens of Spirifer 

 disjunctus var. animasensis Girty are, width to height of area i : .23 

 to I : .36; height to width of delthyrium i : .75 to l : i. 



The specimens from the Three Forks Formation have from thirteen 

 to twenty-one simple radiating plications on each side of the fold, and 

 from nine to fourteen bifurcating plications on the fold. The presence 

 of traces of striae on some of the plications shows that this form is more 



