ADDENDA. 
417 
Spirifera whitneyi. 
Spirifera whitneyi: Hall. Geological Report of Iowa, p. 502, plate 4, f. 2.-1859. 
This species is referred to on page 245, as derived from beds of the age 
of the Hamilton group, in Iowa. More recent observations, with pretty 
extensive collections made in several localities in Iowa, by Mr. It. P. Whit¬ 
field in 1866, have led to the conclusion that this species, together with its 
associates in the same locality, are of higher beds than those of the Hamil¬ 
ton group and should properly be referred to the age of the Chemung. 
Some further notice of the species thus associated, will appear in the 
State Cabinet Report. 
Spirifera nsesastrialis. 
PLATE LII, FIGS. 14-22, 
This species, in its varieties of form, has heretofore been referred to the 
Chemung group only. More recent collections, with better knowledge 
of the limits of the Chemung and Hamilton groups in the eastern part 
of the State, have shown its occurrence in the two formations. The speci¬ 
mens from Schoharie county are from rocks of the Hamilton group, and are 
separated from those in Delaware county by almost non-fossiliferous beds of 
several hundred feet in thickness. It is a little remarkable that while the 
geographical range of the species is less than two hundred miles, its vertical 
range should be so very great. 
Miiynclionella (Stenocisma) contracta var. saxatilis. 
PLATE LIY A, FIGS. 44-51. 
Among the collections from Rockford, Iowa, there are some specimens of 
Rhynchonella, which possess many of the characteristic features of R. con¬ 
tracta of the New York Chemung group, and also those of R. eximia 
of the same formation. The examples figured on plate 54 A, figs. 44-49, 
have much the appearance of the former species, except in size, while the 
[Paleontology IV.] 54 
