10 



POTERIOCRINUS SALIGNOIDEUS (n. s.) Body small, deeply cup- 

 shaped, height about the same as the width at the arm bases, spi-eading 

 very gradually with a slight outward curve from the base, which is 

 truncated and excavated for the attachment of the column, which latter 

 is proportionally large ; basal plates rather short, bent up abruptly 

 at their outer edges ; subradials moderately large, higher than wide, 

 three hexagonal, and two heptagonal ; first radials a little broader 

 than high ; arm facets sub-semicircular, with a broad notch in their 

 upper margins, prominent, occupying a little more than one-half the 

 width of the plate, the upper edges of the plates between the arms 

 slightly bent in ; second and third radials small, about equal in size, 

 wider than high ; fourth radial of about the same size as the second 

 and third, but is pentagonal in outline and supports the arms, and 

 from which they diverge rather abruptly ; above this the arms, which 

 are long and slender, again bifurcate three or four times. Siu-face 

 smooth or finely granulose ; sutures not distinctly marked. Resem- 

 bles P. tenuihracMatus of Meek and Worthen, but the body is less 

 globose in form ; the arms are not so broadly rounded on their backs ; 

 each ray has four primary radials, the anterior one in their species 

 having five ; the second division of the arms takes place on the third 

 piece from the fourth radial, while in their species this division takes 

 place on the fourth piece. 



Locality and position, in the upper division of the Burlington Lime- 

 stone, Burlington, Iowa. — Collection of Mr. Charles Wachsmuth. 



PoTEEioCRiNUS BURS^FOEMis (n. s.) Body in the form of an in- 

 verted, truncated cone, spreading directly to the arm bases, where it is 

 broader than the height ; basal plates of moderate size, bending upward 

 in a direct line with the other plates ; subradials about as high as wide, 

 three hexagonal, and two heptagonal ; first radials much wider than 

 high, almost straight across their upper edges, the second radials occu- 

 pying the full width, and are, with the exception of the anterior one, 

 short and pentagonal, supporting an arm of six broad, short plates on 

 each of their upper sloping sides, above which they again bifurcate 

 once or twice ; second anterior radial quadrangular, about as high as 

 wide ; third and fourth short, more than twice as wide as high, the 

 latter largest, and supporting two arms, which bifurcate twice, mak- 

 ing six arms for this ray ; the full number for each of the other rays 

 seems to have been eight, making thirty-eight arms in all. The 

 arms, except at their upper ends, are flat on the back, and join each 

 other closely at their sides, as in Bursacrinus, except at their upper 

 ends. Anal plates three, or more (?) ; first pentangular, and situated 

 partly beneath the right posterio-lateral first radial. Surface smooth, 

 or finely granulose ; suture lines not very distinct ; column round, of 

 medium size. 



