REPORT ON PAL^ONTOLOGIC 

 Spirifer oameratus, 



plicated, and usually have a narrower area. The plications of the I'tah specimens 



are also generally less distinctly fasciculate, though thev vary in this respect BOmewhat 



In some respects our shell resembles a form figured In Prof Marcou in his work 



So far as yet known Spirifcra camcratus of Morton, is, in this country, peculiarly 

 characteristic of the Coal-Measures, and can always he distinguished at a' glance from 

 any of the forms occurring in our Lower Carboniferous rocks. It is an interesting 

 fact, however, that they find in the Lower Carboniferous series of the ( >ld World, tonus 

 regarded by the most trustworthy authorities as varieties of Sj,irifrr striatus, Martin, 

 which are apparently undistinguishable from Morton's S. camcratus. One of Mr. Da- 

 vidson's figures of S. striatum var. uttotiuttus (tig. 13, pi. II), given in his admirable Mon- 

 ograph of the British Carboniferous lkachiopoda, published by the Pahvontographical 

 Society, is almost as good a representation of some specimens of .Morton's S. camcratus 

 as could be drawn; while Mr. Davidson, whose opinion is worthy of the fullest confi- 

 dence, says he finds so many gradations between this form and the large varieties of 

 S. striatus, with coarser, uniform plications, that they cannot be considered distinct 

 species. Yet it is very remarkable that we should have in the Lower Carboniferous 

 rocks of this country very closely alKed representatives of the large varieties of 8. 

 striatus (if not indeed that species itself*), and in the Coal-Measures others scarcely 

 if at all distinguishable from S. striatus var. attenuatus, while we find no connecting 

 links between these forms at either of these horizons, nor in any of the beds of pas- 

 sage between them. 



Locality and position.— Summit Spring Pass, east of Long Valley, and between 

 Long and Ruby Valleys; latitude, 39° 33' to 40° north, longitude, 115° 12' to 20' 

 west. Position, same as last. 



- See Sp. Logani, Hall, Iowa Report, vol. 1, part 2, pi. 21, fig. 1, 2, 3. 

 45 bu 



