LOWER CARBONIFEROUS FOSSILS. 553 



about twenty other plications, which (on the cast) gradually become finer 

 and more obsolete until the}* disappear and the extreme alar portion is 

 smooth. I know of no type with which this can aptly be compared 

 except S. forbesi, of the Burlington group. 



Formation and locality: Madison limestone, east slope of Survey 

 Peak, Teton Range; S. L. Penfield. 



Spirifer sp. 



A solitary specimen, not referable to any of the forms yet recognized 

 in the Yellowstone National Park. It is a large shell, probably when 

 complete not less than 63.5 mm. wide by 44.5 mm. long; a ventral valve. 

 There is a broad, shallow sinus, which, together with the wings, appears to 

 be covered by comparatively fine, obscure, radiating strise. The entire 

 rostral cavity is filled with shell deposit, as in S. plenus, of the Burlington. 

 Externally this form approaches Syringothyris; the beak is erect and the 

 whole shell has what may be called a hemiconical shape; but it is 

 developmentally not a true species of that genus. 



Formation and locality: Madison limestone. Snake River Valley, west 

 of Two Ocean Plateau; W. H. Weed. 



MARTINIA McCoy, 1844. 



Martima rostrata n. sp. 



PL LXN, figs. 5a, 56, 5c, 5d, 5e, 5/, 5g. 



Athyris planosulcata Hail and Whitfield, 1877 (pars): King's U. S. Geol. Expl. 40tb 

 Par., Vol. IV, p. 257, PI. IV, fig. 10. 



Shell large, obese, lozenge-shaped; when young, wider than long; 

 when old, length and width about equal. Ventral valve productiform; 

 beak prominent, incurved over a moderate-sized area. Foramen large, open. 

 Hinare line half or three-fourths the whole width of the shell. Surface 

 smooth; marked by a shallow sinus extending to the extremity of the beak, 

 where it is defined; less marked below and accompanied by a flattening of 

 the whole valve. Dorsal valve rounded behind, converging in front in 

 somewhat straight lines, whose junction is anticipated by the truncation of 

 a very low fold. Beak prominent, but not produced. Transverse curva- 

 ture gentle and even, or sometimes formed by the two planes of an obtuse 

 dihedral angle, whose edge is the median line. Highest point is at the umbo. 



