NATURAL SCIENCES OF PHILADELPHIA. 139 



others. First radial plates somewhat larger than the suhradials, wider than 

 long and pentagonal in form ; facet for the reception of the second radials 

 moderately prominent, a little concave, and from one-half to two-thirds the 

 breadth of the plate. Anal plates three, the first (or suhanal piece) hexagonal, 

 and resting between the upper sloping sides of two of the subradial pieces, 

 while another on the left rests against this, and upon the superior truncated 

 side of one of the subradials. A third piece is supported on the upper trun- 

 cated side of the subanal piece, and projects more than half its length above 

 the first radial on its right. The succeeding primary radial pieces after the 

 first, are distinctly smaller, and a little wider than long. In all excepting the 

 anterior ray, where the bifurcation takes place on the fifth plate, the first divi- 

 sion of the arms takes place on the fourth primary radial. Above this the 

 arms, which are very long, slender and rounded, divide again on the fourth 

 piece, after which the divisions bifurcate three or four times, and become 

 very attenuate. Each division is composed of a single series of pieces, usually 

 about twice as long as wide. 



The proboscis connects directly with the anal plates already described, and 

 is made up of hexagonal plates, along the sutures of which, distinct vertical 

 ranges of rather large and distinct pores are seen. The entire surface is finely 

 granulose. The sutures are linear and not grooved or impressed. This spe- 

 cies is similar to P. calyculatus of Hall, but may be at once distinguished by 

 its sutures not being excavated, and by its much more slender arms, which 

 are composed of elongate, instead of short wedge-formed pieces. 



Locality and position. Burlington, Iowa. Burlington Limestone. Collec- 

 tion of Mr. Charles Wachsmuth. 



Poteriocrinus carinatus. Body small, basin-shaped or rather rapidly 

 spreading below the arms. Base very small, having the form of a pentagonal 

 star, the angles of which project but slightly beyond the column. Subradial 

 pieces small, about as wide as long, four of them hexagonal, (the form of the 

 one on the anal side is not distinctly visible in the specimen examined ;) all 

 rather prominent, and provided with a vertical carina near the upper angle. 

 First radial pieces about twice as large as the subradials, as wide again as 

 high, and pentagonal in form, the upper side being truncated, and longer than 

 either of the others. Second radials slightly larger than the first, wider than 

 high, quadrangular, and a little constricted around the middle. 



Third radials about the size of the first, pentagonal in form, and like the 

 second slightly constricted, the upper angles being rather salient. The anal 

 plates are not all preserved in the specimen before us, though we can see that 

 the first or subanal piece is of moderate size, pentagonal in form, and extends 

 so far down between two of the subradials, as to connect (apparently) by a 

 very short side, with the produced extremity of one of the basal pieces. Its 

 right superior sloping side supports one edge of a first radial above, and it 

 evidently supported another piece on its superior truncated edge, while it 

 connects on the left with another resting on the upper truncated side of one 

 of the subradials. 



After the first division of the third radials some of the arms bifurcate again 

 on the fifth, sixth or seventh piece, while others seem to be simple. They 

 are all composed of pieces which are a little constricted around the middle, 

 as long as wide, and alternately longer and shorter on opposite sides, the 

 upper extremity of the longer side of each being a little projecting for the re- 

 ception of the tentacles, so as to give a zigzag appearance to the arms. The 

 tentacles are large, and composed of rather long joints. Owing to the length 

 of the arm pieces, and the fact that only every alternate piece on the same 

 side supports a tentacle, they are very widely separated and alternately ar- 

 ranged. 



The surface seems to be granulose, and each ray is provided with a distinct 

 linear carina, commencing on the middle of each first radial piece and extend- 



1861.] 



