31 



Family POTERIOCRINIDiE. 



POTEltlOCRINUS CIRCUMTEXTUS, n. sp. 



Plate II, Fig. 29, azygous side, showing the interlacing arms 

 and proboscis; Fig. SO, opposite side of same specimen. 



Species medium size, with a remarkably large proboscus. Cajyx 

 cup-like, or somewhat obconoidal; truncated below for a moderately 

 large column; wider than high; sutures distinct; surface smooth or 

 very finely granular. 



Basals one-fourth wider than high, pentagonal, gradually ex- 

 panding. Subradials about as long as wide, three hexagonal and 

 two heptagonal; those adjoining the azygous area are heptagonal. 



First radials of unequal size, but about twice as wide as high, 

 protuberant and rounded to the first brachials; hexagonal; the 

 articulating scars occupy rather more than half the diameter of 

 the plates and are directed outward and upward at an angle of 

 about seventy degrees; a slightly gaping suture separates the first 

 radials from the first brachials, and the superior faces of the first 

 radials unite with the small plates that cover the vault. 



There are four brachials in each of the latteral rays and three 

 in each of the other three rays; they are short, rounded, and the 

 last one supports upon each of its upper sloping sides free arms. 

 All of the arms again bifurcate on the fourth plate, except one, 

 and it bifurcates on the fifth plate. Every arm bifurcates again 

 on plates ranging from the sixth to the sixteenth. At this height 

 there are forty arms; some of them are seen to bifurcate again in 

 our specimen, and probably all bifurcate again, making eighty 

 arms in the species. The arms are rouud, plates long and sutures 

 transverse. 



The azygous area is wide and ventricose. The first plate is 

 pentagonal, rests between the upper sloping sides of two sub- 

 radials, separates the first radial on the right from the second 

 azygous plate, and is truncated above for the third plate. The 

 second plate is hexagonal, rather larger than the first, truncates a 

 subradial, abuts the first radial on the left and the first and third 

 plates on the right and supports two plates above. The third 

 plate rests upon the first and is in line with the upper half of 

 the second, supports two plates above and other plates on the 



