62 OWEN AND SHUMARD'S FOSSIL CRINOIDEA. 



with the undulating edges of the plate, forming a series of hexagons, one within the 

 other, giving to the whole surface an exceedingly neat and elegant appearance. 



Superior plates six, of which five are elongated, quadrilateral, rounded at the 

 inferior edges, and support the arms ; one is trapezoidal, wide, slightly angulated 

 below and narrow above. The articular surfaces for the arms, situated on the 

 superior edges of the five arm bearing plates, are moderately large, very slightly 

 excavated, striated on the margin, with a transverse ridge near the centre. All the 

 superior plates are finely corrugated on the external surface. 



Arms. — Several joints of the arms remain attached to one of the superior plates, in 

 the only specimen we have been able to procure of this species. The first joint is of 

 a rectangular form and supports a cuneiform joint, on the bevelled edges of which is 

 the commencement of two series of smaller plates. Each of these joints is distinctly 

 corrugated on the dorsal surface. 



Dimensions. — Height 9 lines, greatest width 8 lines, diameter at summit 6 

 lines. Height of pelvis 3 lines, do. of superior plates 5 lines. 



The column is undiscovered. 



This is one of the most beautiful species with which we are acquainted. It was 

 obtained from the quarries in the carboniferous limestone at Burlington, where it is 

 exceedingly rare. 



DiCHOCRINUS STRIATES. (NeW Sp.) 



PI. 7, fig. 10, a, h. 



Body globose and composed of thin plates. 



Basal plate hexagonal, bi-partite, hemispherical, superior margin undulating ; circle 

 of attachment for the column small, slightly excavated, finely striated in radii, with a 

 minute round perforation in the centre. The surface is marked with permanent 

 thread-like strise, some of which begin at the excavation, others originate near the 

 middle of the plate, and radiate to the superior margin. 



Superior plates six, five of which bear the arms; these are quadrilateral, somewhat 

 elongated, wider inferiorly than at the summit, with the articulating surface for the 

 arms, as in the preceding species, situated on their superior edges. The non-ray- 

 bearing plate is trapezoidal, wide, slightly angular at the base and narrow above. 

 The striae on this series of plates range in lines parallel to the lateral borders and 

 join those in the basal plate. Some of the stria? are bi-furcated near the upper margin, 

 and when examined with a lens have an undulated appearance. The furrows 

 between the striae are crossed at irregular intervals by transverse threads. 



