FOSSILS OF THE DEVONIAN. 



143 



Spirifera (M.) undifera Eoemer. 

 Plate iii, figs. 3, 3 a, I, 6, 6 a; plate xiv, figs. 11, 11 a, b. 



Spirifer undiferus Eoemer, 1844. Rhein. Uebergaugseb., p. 70 u. 73, tab. iv, figs. 5, 6. 

 undiferus Schnur, 1853. D linker's Palaeoutographica, vol. iii, Bracli., Eifel., 

 p. 204, tab. xxxiv, figs. 3 a-d. 



Sandberger, 1855. Bracb., Ehein, Schichtensy stems, p. 18, pi. xxxi, 



fig. 8. 

 Spirifera undifera Davidson, 1865. Mon. Brit. Devon. Brach., p. 36, pi. vii, figs. 1-10; 



also, var. undulata, ibid., figs. 11-14. 

 compacts Meek, 1868. Trans. Chicago Acad. Sci., vol. i, p. 102, pi. xiv, figs. 



llo-d. 

 undiferus, var. Talcwancnsis, Kayser, 1882. China, Richthofen, vol. iv, p. 86, 



tab. xi, figs. 1, 1 a-e. 



Compare Spirifera Jimbriata (Conrad, 1842) Hall, 1867. Pal. N. Y., vol. iv, p. 214, pi. 

 33; also, 8. snbundiferus M. & W., 1868. Geol. Surv. Illinois, vol. iii, p. 

 434, pi. x, figs. 5 a-e, and S. (M.) Richardsoni Meek, 1868. Trans. Chicago 

 Acad. Sci., vol. i, p. 104. 



But one specimen of this species was found among- the Devonian 

 Brachiopods brought from the Eureka District in 1880. That differed so 

 much from a typical specimen of Spirifera (M.) undifera, kindly sent to me by 

 Mr. Davidson, who received it from Dr. Roemer, that I gave it a specific 

 name in manuscript, comparing it to (M.} fiwibriata Conrad. During the 

 field season of 1882 a large number of specimens were collected from the 

 Lower Devonian of the same district that afford the means for a more 

 extended comparison with S. (M.) undifera and S. ( M. .) Jimbriata. 



The variety shown by figs. 11,11 ab, of plate xiv (the original speci- 

 men found in 1880), has the beak of the ventral valve so closely incurved 

 that the narrow area and the foramen are almost entirely concealed; the 

 few broad, rounded plications are crossed by concentric striae, with inter- 

 spaces between of a little over one millimeter in width; on these, between 

 the striae, radiating interrupted striae occur that are precisely similar to those 

 on specimens of (M.)fimbriata Conrad, now before me, from the Upper Hel- 

 derberg Group of New York, except that they are somewhat finer. On the 

 shells of this species from the shales of the Hamilton Group these radiating 

 striae reach their maximum development, appearing as elongate, radiating 

 tubercles on the interspaces between the imbricating striae. Among the 

 Eureka specimens individuals occur that show the concentric striae about 



