NATURAL SCIENCES OF PHILADELPHIA. 69 



more inclined to round in to the column below, but not near so much so as in 

 the last described species, from which it also differs in having much shorter 

 arms. 



Locality and FosUion. Lower Burlington beds, Burliugtou, Iowa. Lower Car- 

 boniferous. No. 33G of Mr. Wachsmuth's collection. 



Genus DICHOCRINUS, Munster, 1839. 

 DiCHOCRiNus LiNEATus, M. and W. 



Body ovoid-subglobose, about as wide as long, not rounded below, but 

 abruptl}' tapering to the column ; widest near the middle, and but slightly 

 contracted above. Base forming very nearly half the height, and expanding 

 rapidly, so as nearly to equal, at the top, the greatest breadth of the body ; 

 margins faintly sinuous for the reception of the next range of pieces ; sutures 

 a little furrowed, but anchylosed. Radial pieces quadrangular, generally 

 nearly or quite as wide as long ; sinns above, for the reception of the second 

 radials, shallow, rounded, and equaling about half the breadth of the upper 

 margin, marked with fine radiating strise at the outer margin. Anal piece as 

 wide below as the first radials, but narrower above, and slightly shorter ; sub- 

 pentagonal in form, being but very obtusely angular in the middle below. 

 (Succeeding parts unknown.) 



Surface ornamented with numerous sharply elevated lines, slightly less than 

 the furrows between. Of these lines, on the base, a part near each lateral 

 margin run parallel to the same ; while other series farther from the margins, 

 although parallel with each other, on each side of the middle, run obliquely 

 so as to connect with the lateral ones, and with each other, along the middle, 

 in such a manner as to form three divaricating series on each piece : near the 

 upper margins there are also traces of a few very fine crowded striie running 

 parallel to the same. On the first radial and anal plates there are also a few 

 fine transverse stri^, near and parallel to the lower margins; while on a tri- 

 angular central space, with its most acute angle terminating near the middle 

 of the top, there are vertical or slightlj^ converging striae of the same size as 

 the divaricating series on the base ; and on each upper latter space, on each 

 side, anotlier series runs tip and down, parallel to the lateral margins. Column 

 rather small, round, and provided with a very minute central perforation. 



Height of body to top of first radials, 0-65 inch ; breadth, 0-Gi3 inch ; height 

 of base about 0-30 inch. 



This species seems to be somewhat intermediate in its characters between 

 D. ovatus and D. slriatus, of Owen and Shumard. From the first it differs in 

 having distinct, sharply defined, continuous lines on the body plates, instead 

 of merely rows of depressed granules ; and these lines also run diff"erently on 

 the basal pieces from the rows of granules on that part of D. ovatus, which are 

 described as forming a series of hexagons, one within the other, instead of 

 forming three series of triangles, as the lines on our species show a tendency 

 to do. The lines are also as well defined on the radial and anal pieces of our 

 species as on the base, while the surface of these parts of D. ovatus is described 

 as being merely " corrugated." 



In having continuous, well defined, raised lines, it agrees more nearly with 

 D. striatus, of Owen and Shumard ; but it is easily distinguished from that 

 species by having these lines very much finer and more crowded, as well as 

 greatly more numerous, there being about ten of them in the space of 0-20 

 inch, which only includes four or five of those on Z>. slriatus. 



Locality and Position. Lower Burlington beds, Burlington, Iowa. Lower 

 Carboniferous. Mr. Wachsmuth's collection. 



DicHOCRiNcs pisuM, M. and W. 

 Body small, somewhat cup-shaped, approaching sub-globose, rather de- 

 pressed or flattened below, and from one-fourth to one-third longer than wide, 



1869.J 



