EEPOET ON PALJflOBTTOLOGlCAL COLLECTIONS. 351 



in a condition to show the interior; but, so far as can be determined, they present no 

 external differences from Professor Mall's species. 



This seems to be one of the most widely distributed species of all those known in 

 the Carboniferous rocks. It ranges from Eastern Ohio, through Indiana, Illinois, Mis- 

 souri, and Kansas, westward to the middle of the ( Jreat Salt Lake Basin, and from 

 Nebraska far into Xew Mexico. Mr. Marcon also savs he has received it from Van- 

 couver's Island;* and Mr. Davidson identifies it from the Carboniferous rocks of 

 England, as well as from India, and it also occurs in South America. 



It is a little remarkable that in this country Atht/ris xnhtiVitn is, so far as known, 

 peculiarly characteristic of the Coal-Measures, while in En-land it appears to occur 

 only in the Lower Carboniferous rocks. Mr. Davidson once referred it to the genu*} 

 Terch-atula, with a query, not having- seen the interior. Several of the specimens, 

 however, found by Dr. Havden and the writer in Eastern Kansas, in the same beds 

 from which those 'first described by Professor Hall were obtained, show the internal 

 spiral appendages and other characters of the genus Afhf/ris, or Splrit/mi, as it may 

 have to be called. 



Genus SPIRIFER, Sowerby. 



Spirifer (Spiriferina ?) scobina, Meek. 



Plate 2, fig. 5, a, b, c, 

 Spirifera scobina, Meek (July, 1860), Proceed. Acad. Nat. Sci., Philad.,XII,310. 



Shell rather large, truncato-subcircular, approaching subpentagonal, moderately 

 gibbous, length and breadth nearly equal, hinge-line scarcely equaling the greatest 

 breadth; lateral margins rounding anteriorly and intersecting the hinge almost at 

 right angles; valves nearly equally convex, each provided with from about seventeen 

 to twenty-two rather broad, depressed, occasionally bifurcating, plications. Ventral 

 valve a little more gibbous than the other, and having a shallow mesial sinus, which is 

 very small near the beak, but widens gradually toward the front ; beak moderately 

 prominent, incurved; area of medium breadth, with nearly parallel margins, extending 

 to the lateral extremities oi' the hinge, distinctly arched near the beak; foramen having 

 nearly the form of an equilateral triangle. Dorsal valve moderately convex in the 

 umbonal region ; beak rather prominent and incurved ; mesial fold depressed, not dis- 

 tinctly defined excepting at the front, where it is generally flattened. Surface of both 

 valves apparently without striae, but beautifully ornamented by numerous minute 

 regularly disposed granules. 



Breadth, 2 inches; length, 1.88 inches; convexity, 1.34 inches. 



From about three to five of the plications usually occupy the mesial sinus, and 

 near the same number the mesial fold, in the former of which they are generally a 

 little smaller than on each side. On some specimens most of the plications are simple, 

 while in other instances a portion of them bifurcate, though rarely more than once. 

 The plications are usually about twice as broad as the grooves between. The mesial 

 sinus is never very strongly defined, and sometimes becomes almost obsolete near the 

 beak. Where the surface has been a little worn, the fine granules are entirely oblit- 



* I think this an error, however, as I have never heard of any other evidence c 



